How can we find a middle ground?

I would personally say something like "I know you don't like it when I bring this up, but it is truly affecting our marriage and family time. I feel like you are spending too much time on your hobbies and making that a priority INSTEAD of making me and our son a priority. I married you and had a child together so we can raise him together, not alone like I feel I am. I want you to enjoy your hobbies, but it becomes a problem when you spend too much time on them. A healthy life and relationship is when you have a healthy BALANCE between your hobbies and family life. I feel like you are putting more effort and time into your activities instead of us, and it's honestly hurtful. I want to read our son stories and tuck him in TOGETHER, I want to shop for the great food you bake TOGETHER. I'm proud of your Crossfit achievements and want to continue to support that and cheer you on, but you need to do the same and give me and our son the same kind of time and attention." Just be honest and tell him exactly how you feel. 

Let him know that going forward you want equal time to pursue your own hobbies. So if on Saturday he spends all day baking, you get Sunday to not do any household duties and spend the day doing whatever you want. If he spends 4.5 hours at the gym after work three days a week, you take three days to LEAVE THE HOUSE for an equivalent amount of time to do whatever you want. The leaving the house is key, because that way you don’t get roped into doing default childcare or house things simply because you’re physically there. If he isn’t okay with that, you have an opening to start your discussion about why it is okay for him but not for you, and point out how unfair the current setup is.

Don’t let him twist it around and manipulate things. CrossFit might be good for him, but it’s not good for you (plural) if it’s creating resentment like this. Bottom line is that people treat you how you let them, you’ve allowed this behavior, so changing it is going to be difficult. Not impossible, but probably very uncomfortable. Professional counseling could help you navigate this.

Don't eat what he bakes. ( He might learn what it means to be Unappreciated)

Plan fun activities with your son, scheduled when he's at the gym. (He might learn what it means to be left out).

Do not guilt him for not spending enough time with your son. Society always remind us these things. 

If you use guilt, it's going to sit in his head, pressuring him to do something he probably doesn't even know what to do.

It's not like a child comes with a manual. 

Just because you read and do other things, doesn't mean your partner feels like himself doing this.

You want him to want and enjoy time at home. Not do it out of guilt. 

He'll be going home thinking "Oh, God what do I do with a son..." instead coming home and relax.

Its only when the brain is relaxed, much easier to enjoy the process and new ideas come easier.

Besides, why is he training for 4.5 hours? Does he want to become a crossfit trainer?

Or can he make living doing baking?

Did that cross his mind?

If he is the head of the household, then having multiple job options is also important. 

You just need to figure out how to incorporate your family time and his possible career paths, and it's all will be good for all of you.

To find your middle ground,  watch and balance closeness/intimacy and independence. 

When feelings begin to feel "cold", do not let it go to the the point where you want to eat each other's brains out. Do things separately. Recharge and share that with each other.

When you begin to feel like it's not enough love in your relationship - pull each other closer. Do what makes you feel love and loved.

Once you reach to the point of love euphoria, it will begin to fade again making things feel kinda "cold".

Does that sound familiar?

There is really no right or wrong formula for this in terms of time.

It's more about how each of you feel. And you just need to pay attention to it.

For example, right now since your partner has been doing baking and crossfit for so long, you maybe at the point of love-starvation. 

When that happens, it's very difficult to give what you feel depleted of. Your partner feels it, it's not satisfying and he keeps pursuing what recharges him, gives him meaning, pay off.... It's a dead circle, unless he is aware of the problem.

Therefore the first thing I would do is to replenish myself. But you do what that means to you.

Bring all this to his awareness.

Explain to him that you want his focus on you as passionately as when he does baking or crossfit. Ask him what does he need for that? What is missing? 

His answers will guide you to what you also need to do.

Also.

Taking care of children can be very time consuming. Doesn't mean we need to forget of our hobbies and alone time. But it's reasonable to shorten the time spent doing those things until children reach the age when they don't require as much attention and care. 

One supposes that if you're going to eat a lot of baked goods you really do need some kind of workout regimen to not turn into a parade float, jk. If he's amenable to marriage counseling that might help. But you could also appeal to him that your son is growing up with only one involved parent. This is where your orientation might matter in that when same gender couples have kids it's taken a serious decision and affirmative action on their parts. Babies don't just accidentally appear in gay marriages. So maybe remind him of all the effort the two of you put into becoming parents. Remind him that a childhood is brief and that no amount of scones or workouts will replace the memories he's not making with your child. Good luck. 

Next time tell him you aren't mad at 

something that's good for him, you're 

mad at HIM for thinking that he's more 

important than your child and you. He 

needs to decide if a family is his priority, 

or HIMSELF. He doesn't have to give up

that stuff if he feels that is more important, 

but he is making it very clear where you 

and your child stand in the order of things. 

You're not "mad at something that's good for him." You are asking him to be an equal partner in your marriage and in parenting your child. You know what would be good for YOU? Having a husband who isn't self-absorbed and actually prioritizes his family once in awhile. When do you get something for yourself? Relationships are about compromise, not one person doing whatever they want while the other handles all the responsibilities. 

Maybe make up a list of what errands need doing every week - things like groceries, laundry, bedtime for kiddo, paying bills, meal prep, etc, and how much time it takes to do each thing. Highlight it in yellow or whatever. Then make a list of "me" time you both get. Highlight his in green, yours in blue or whatever. Basically, create a chart that visually represents how much of the household burden you carry, and how little time you get for yourself or how little time the two of you get together as a couple or as a family. When someone really SEES what is going on, it might help. (ps I had to do this with my husband)