With your financial situation this option may not be possible but if I were you, I'd go buy an XR 100 or similar. Ride the crap out of that on your BF's parents property for a month or 2 then go back to looking at bikes. If I'm understanding correctly you just need to learn how to ride from the very beginning. Shifting, turning etc. Do that on something that doesn't weigh twice what you do but will still teach you the basics. From there I'd step to a KLX 250 (lower it) or similar. I had a buddy that bought a TW bacause he's inseam challenged. 55mph maybe 60 and that was pushing it and the DR 200 ain't much better. He ended up putting only 600 miles on it in a year and half. But maybe, just maybe when you get all the basics down, the DR 650 won't feel to crazy because after all the basics, shifting, turning, etc are down pat the weight of the DR 650 will fade. When you finish with the XR 100 you can sell it for what you paid for it so no money lost to learn or pass it down to the kids.
I'm not to proud to say, back 6 years ago when I started riding, I signed on the dotted line on a brand new 07 ZX6R. Brought it home rode it up the dead end road at my house and pulling back into the driveway at about 3mph proceeded to completely drop it because I didn't have a clue what I was doing. Talk about a moment, 10 grand that was new half an hour ago was laying on it's side in my driveway. Hopped back on and in the next year upped my skill level pretty good but we all start out at the moment where you are. Especially if we start doing this later in life. Just don't loose your nerves.
The other way you could go is a Zuma 125 scooter. It's a light, twist and go option. tops out at about 60ish but will do 55 mph all day long. Yes they will offroad.