I don't know why I wasn't expecting that clip.

The problem with this is that science has no incentive to "cure obesity." Treating every intersecting condition it a trillion dollar industry, that's before we even get into the diet industry which funds all the research.
It would be awesome if they did, so our only weight related medical worry would be immobility.

As an FA I can say I've always found fat more attractive.

Not a feedee but as a gainer I can say that I didn't always want to be fat but the more fat role models I had the more I wanted to be fat too.

So as they've already advised there are 2 ways to work on this.
One is getting yourself a mobility aid like a wheelchair or scooter, which will deal with the issue most the time but doesn't help in those times you have to get up from it.
The other option is to work in some light exercise to strengthen your legs. Swimming is the best option, the water takes much of the strain off your joints. Laps are fine but if you wanted to try squats or lunges in the shallow end the water would definitely make those easier. If you think you can keep up a water aerobics class is generally designed with someone with joint issues in mind.
Regardless of how you choose to go, for the foot pain I'd advise visiting you local running shop and getting a good pair of shoes. You will feel out of place there but they'll have shoes meant to pad the foot under some serious pressure which it sounds like you need.
For the weak knees in the mean time consider a bariatric cane. I know nobody ever wants that option but it sounds like you need extra support on the left side and that will give it to you.

It is attainable, I'm up 60 pounds since last thanksgiving.

I've always wanted to be fat, though the level of how fat I wanted to be changed a lot.

As a kid I always preferred fat, probably because there were a lot of fat couples I looked up to. The women were smart and beautiful and all had equally fat or fatter partners. So naturally I wanted to be fat.
What probably set my goal though was a couple that came out to our local pool. She was probably pushing 400 and he had to be in the 500s. She paid several of us with food to go get snacks, mostly for him. I was always mesmerized by his huge belly, it hung below his knees and when he sat down it could rest on the ground. I knew immediately I wanted one just like it.

Fast forward a few years and I realized I only needed 30 pounds to break 200, so I started seriously overeating. I learned that I loved being absolutely stuffed and 200 wasn't near as fat as it seemed. So I set my eyes on 300, cause sumo wrestlers are that size and they're huge. It took several more years to hit that goal.
Still don't have the belly I want so I'll keep gaining. Goals have moved from 300 to 400 to realizing I probably need to hit the 600s for the look I want.

Personally I've always recommended 20-25 pounds because by that range it should be publicly noticeable and see if you're still interested once people start to notice.

Trying this today, I only got the king size ones since those were the most available. Regular and funsize combined totalled 5 where there were 20 king size at my local Wal-Mart.

I can't speak for others, but I just sit because that eliminates the need to do anything more than unsheath if necessary.

Saggy breasts are awesome. Being effected by gravity is nothing to be self conscious about. Unless you stay quite small or pay a small fortune to combat it everyone's breasts sag eventually. Just look through the pics here and you'll see you're in good company here.