Were do I start when trying to get back into dirt biking?

Rick, your biggest problem is your bike keeps getting sold out from under you and that must rip you apart. I really don't see much point in a repeat of that so if I was you I would want to sort that out first. Take an honest look at why it happens and talk it out without any agro. I'm guessing here that a parent has a part to play in the sale of the bikes in the past, but what brings that on to get to that point? When you have worked that issue out I would look for a bike but not before then,,,,

sit on it

You should start with an 85. It's not too big nor is it to small it's just right for your age and height.