I’m not vegan so I don’t really have many suggestions in that regard, but our stats are pretty similar! As for exercise would you maybe be able to do a stationary bike at the gym? These are fairly low impact and I don’t think they should hurt your knees much but I could be wrong. Amazon even has mini pedalers that you can do at home to burn a few calories. Something like this https://www.amazon.com/Drive-Medical-Exercise-Electronic-RTL10273/dp/B002VWJYSE/ref=sr_1_4_a_it?ie=UTF8&qid=1489422490&sr=8-4&keywords=mini+pedal+exerciser
https://www.amazon.com/gp/product/B002VWJYSE/ref=ppx_yo_dt_b_asin_title_o07_s00?ie=UTF8&psc=1
It's not going to give you the same workout as a full bike, obviously. It puts up no resistance. But I use for a couple hours a night and it is helping me lose weight.
I've been considering getting one of these. It's a pedaler, I can sit and pedal (I think some people also use it to pedal their arms), and some fold up so they're good for small homes.
I hope I'm not too late to this thread - for people that don't have an exercise bike, I use one of these - peddler It is foldable and very simple to use.
I have this one. It's decent for the cheap price! And it folds up small. https://www.amazon.com/dp/B002VWJYSE?ref=ppx_pop_mob_ap_share
word of warning, mine gets very hot if you use it for more than 20 minutes. i have been using it for 15, resting 5, then continuing.
Could get something like this and put it under your desk
This one works great with LiveSplits : https://www.amazon.com/Drive-Medical-Exercise-Electronic-RTL10273/dp/B002VWJYSE/