About bike replacement, I'd say do what you have to to keep wanting to ride. Keep it fun so you keep coming back to it. I don't have to tell you, but exercising is such an important part of living well that I think it justifies investment if you can swing it in the first place.
Congratulations on your weight loss, that's very impressive. I'm a Clyde myself, and the biggest loss I've managed is 45lbs. That took nine months. You really turned in a superior performance. (Thanks to a medication change I just picked up 10lbs in two months, so back to weight reduction again.)
I'm back to riding as an adult after 20 years away. The two things that I had to see to believe are 1) how easy it is to steal a bike and how often they get stolen, even when locked up -- a huge problem IMO that you have to worry about and 2) how distracted drivers are these days, with phones and touch-screen dashboards and our crazy lives. Something to think about.
Welcome back!