Chances of sole custody and additional supports?

In contemplation of leaving you should see a lawyer specializing in Family Law. That is the one place you will get solid legal advice. Anything on here is just so much couch lawyers advice. If you are serious about taking that step that IS what you need to do. 

Hopefully they can answer this sort of question and many more that you might have. And also some of which you might not have thought of at all. 

But here is some advice I can give you - 

1. Document EVERYTHING. Date, time, what was going on, what she was doing (or not doing) and what she said about it. This is when it concerns her attitude towards you as much as it does her attitude towards your child. Anyone who may have witnessed the behaviour. Your child's reaction to it. Any doctor's reports, any daycare staff concerns, etc.  When you are caring for him, and what you do then. A clear record of when and why is a lot better than "Well,  sometimes she would....". 

2. Gather any relevant paperwork (or copies) - bank records (yours and hers), credit/debt details, insurances, receipts for valuables and serial numbers (or photos), superannuation paperwork, any stocks or bonds, current bills, important paperwork, passports, etc. 

3. Do NOT give her ANY ammunition against you. Be civil and polite - kill with kindness. Do NOT put anything in writing that she can use against you - texts, emails, social media, etc. Yes that can be hard but ignore this rule at your peril. Do not act angry outside your home. Be careful on the phone, not just to her but to those connected with her. Do not allow her to provoke you into foolish actions (specially after you hand her the papers). Keep anything from her that can be used by your lawyer too. 

4. Be prepared for a pre-emptive strike IF she ever gets wind of what you want to do. She might start spreading lies/rumours about you. Have all your ducks in a row, and follow number 3 to a tee. 

Good luck. By the sounds of it you may need it. 

Unless there's documented evidence of your wife being violent or neglectful of your son (or if she just chooses to not have any custody) it's unlikely you'll get sole custody. But Australia generally has a pretty generous social safety net for single parents. Depending on your wife's income she may also have to pay child support to you if you were able to get sole custody. 

Your chances of getting custody of a 2 year old absent documented abuse is about nil. 

Start hiding nanny cams all over, so you have proof of her abuse If you get sole custody, make her pay for day care and his medical. A good lawyer can help you in this case.

Pretty sure Australia has a formula system for determining support, so you can figure that out right now.  It depends on how much each parent earns, and I think, like in Quebec where my CS obligation was decided, includes an aspect for amount of time the child or children have with each parent, but you better look that up.  The government has a webpage that lets you put in the numbers and figure out what the obligations would be.

Having sole custody does not mean that the child has no time with the other parent, although if the other parent is really bad at parenting, that time might require supervision or might be minimal.  Sole custody means that you have primary responsablity for the child and for making decisions that affect the child, that the other parent does not possess.

Is any of this abuse of him or you documented (preferably in a police report)?  If not, it will be your word against hers and hard to prove in court.

In the U.S. it's harder for you to get custody if you don't have your own place or child care means while you work.

Sole custody also doesn't take away her parental rights.  She would likely still receive visitation, even if it was supervised visits.  She'd likely get a court ordered parenting plan which would likely include some counseling/anger management classes and if they visits go well they will eventually change to unsupervised.  

If you were to receive primary or sole custody, you can still petition the court for child support from her.  The only time you can't is if her parental rights are terminated and that takes a lot for that to happen.  I do foster care and terminated parental rights is always a very last resort.  The only time that's expedited is in extreme cases of abuse.

If he already goes to daycare what is the need for additional support?