Over-reaching or progression? (Cycling)?

If you were already very fit, a 20 mile bike ride would present no difficulty at all, particularly if you had already been cycling shorter distances. At lower levels of intensity, fit cyclists can keep riding for about as long as they can stay awake. You appear to have been riding at a fairly low intensity, not nearly hard enough to cause lasting fatigue, and so far your rides haven't been all that long. Keep increasing your mileage as you progress until you can comfortably do a 60 mile ride. At that point you should be able to complete a century. You can expect the last 25 miles to be much harder than you expected, although the last 5 or so should be easy once you realize that you are really going to be able to do it

After many years hardly riding, I am back on the road. I Started in 2011 at the novice level and now I do 2-3k miles a year including several centuries.

In my club we use this system to classify recreational rides:

Novice, less than 11 mph

E 11-13 mph

D 13-15 mph

C 15-17 mph

B 17-19 mph

A 19-21 mph

Currently I ride C easy and can do B with some effort. My routine is T and TH 35-40 miles, alternate Friday or Saturday 45-50 miles, Sunday 75-100 miles. As time and weather allows.

So you are at novice and middle E. Even E riders can do 50+ miles, they just take longer time. It is possible to over-reach but let your significant other relax knowing that so far that is not the case. If any, you are not doing enough to prepare for your century in late fall which is a sensible goal.

For now, don't try to go for speed. Stay where you are but aim for 40-50 miles rides in a couple of weeks, increasing gradually from 20 miles. Build endurance first so you can do 6-8 hours at one go. Now is the time to make adjustments on you bike and riding technique. Learn about cadence and breathing. The weightlifting if you are very bulky can be detrimental as cycling uses and builds lean muscle.

Now, 50 miles if you don't have a proper road bike would be painful and more than that would be almost impossible. Use the right tool for the job.

Edit: Get this book. Even if your goal is not to loose weight, The book is full of valuable information. You would have to ask thousands of questions to figure out everything that is on the book and yo will need all of it.

not sure what the question is

yes you can probably do a century if you can sit in the saddle for 8-9 hours

if you feel ok, you are ok

c. 9, 12 mph is just loafing, start moving that to 15-17 mph averages!

wle

You are doing great and with your history there should be no worries at all. It sounds as though you are simply refining your abilities and your muscles are happy to oblige.

Nothing at all wrong with a multivitamin or fish oil.