Hi
@bacon0339
Some great advice already posted in this thread so not a lot I can add. Sounds like you well and truly have the cycling bug so welcome to our world
It is a good point about seeking out some beginners adult training. If you can find a group or organisation that does this they will hopefully point out any obvious errors in your current bike position/set-up and also any mistakes in your technique such as using gears that are too high/low for the situation. The main aim of these courses is often focussed on teaching you how to ride on the road, how to position yourself at intersections, when and how to signal, etc. Do you drive/hold a driving licence? If you are already an experienced driver then you should already know a lot of the basics as the same rules should apply to a cyclist (when to stop, when to give way, which direction to look for approaching traffic, etc).
I wouldn't be too worried about riding on the sidewalk (I would say pavement as this is what we call it in the UK but I think pavement means road surface in the US?) as long as you are sensible, careful and considerate. Most people will only get aggressive about it if you ride like an idiot and put people at risk, it isn't a race track.
I saw this clip on TV a few days ago, PLEASE don't ride like this moron!
There are plenty of unkind comments that follow the clip but I side with the view that the cyclist was fully at fault here as they had a complete view of the situation and were riding far too fast to avoid what was a fairly predictable incident.