Does anyone have any advice for dating USSBBWs?
Yes, if that's what makes your dick rockhard and that's your ultimate preference, chase them and date them. That said it comes with certain challenges and restrictions. I've had a few 500lbs girlfriends, and honestly as much as the sight of extreme fatness gets me, I wouldn't go choosing to have a relationship with one if i were single. (I ultimately married a woman who was 450 at her heaviest, was maybe 330 when we married and is currently about 280 in her early 40s)
1. Smell? Don't date them. Don't put your dick in crazy, and don't put your dick in a woman who doesn't care for her hygiene. If it's a one night stand fuck your mileage may vary, but I only did it once. My wife is incredibly clean. She changes when she comes in if she's been in the office, she'll have a baby wipe clean whenever she feels she wants to if it's the hottest summer days, she always smells nice
2. They know you're a chubby chaser, they fucking well already know you are, they just want to know how confident you will be to be seen with them. My general line 'label me if you need to, i know i fancy you like crazy'. In all honesty, they're looking for someone who isn't a fucking creep and who isn't wanting to fuck a fat girl to tick it off their list. Let her know you like her and you're not afraid to be seen with her.
3.Yes, hide it at first, don't make it obvious. Don't go straight in grabbing her fat rolls, she likely won't like it, plenty of places to touch instead. You might get lucky and once you've been intimate and she gets it, this guy really likes all my fat, she might invite you there. Plenty to touch elsewhere, she'll thank you for it.
4. Are you actually a feeder, or do you just have aspirations of? Change it back to her, ask whether they're saying they get off on getting fatter. Then you can be a bit coy, 'i like your body, so if you were bigger, fuck, i guess I must be at least an an enabler if i say you'd look hotter even bigger'
5. Introduce her to people who you know aren't gonna be judgemental assholes. Also, be polite enough to forewarn who you are introducing her to , it will probably help you get them on your side. Your parents will always likely be a hard sell. You just gotta let them know this is who you really like.
Lastly furniture, you best get your A game on. 500lbs? They never broke a sofa, we broke a few bed legs on vacation, but the bed was pretty shitty. Trust me, they already know and are looking out for it, they don't want to embarrass themselves. If the girl you posted is what you're after, you've no problems, she's no SSBBW let alone USSBBW.
Good luck if that's what you're after, but go find some hot girl in the mid 300s before you go diving in at the deep end.