Bars: 8,25 to 8,75 should be perfect, one thing you might wanna take into consideration is the amount of upsweep, normally between 1 and 5 degrees, in my opinion more upsweep is easier on the wrist, but maybe you can try out some different bikes at the park to see what you prefer.
Don't get too hung up on street vs. park vs. dirt bikes. The main difference I would say is that streetbikes nowadays have a crazy short backend. I would assume your '03 Fit frame has a 14'' backend, whereas for streetbikes nowadays the standard seems to be 13,25'', so find something in the 13,5'' - 13,75'' region. Anything longer is usually dirt frames and since you mentioned you will be grinding dirt specific frames are maybe not ideal. Also look out for headtube angles, again, I assume your '03 Fit frame has a 74,5° headtube, whereas nowaday you find alot of frames with 75+° headtubes, which makes the front more twitchy, so I would advise to not change it up too much and stick to a max headtube angle of 75°. Part wise the save bet seems to be anything from sunday odyssey or gsport because they are backed with a true lifetime warrantee, so if anything ever happens to your fork frame bars cranks or rims or whatever, you usually get it replaced for free. Have fun getting back into riding!