I'm in need of some brains to pick here. I have been advised by many, including a psychologist friend, that I need a PSD (Psychological Service Dog). To explain, in brief: My social anxiety has been getting increasingly worse this past year, and is now so bad I'm nearly homebound. This is because my biggest trigger is strangers, especially males, getting too physically close to me, and as I cannot drive I must take buses to get anywhere. As I cannot always have a trusted person along with me whenever I go out, a service dog is my best option.

Here's the problem (or rather, several) - I live in a 748 sq.ft. 1 bedroom apartment with 2 snakes, a BTS, a bunny, and my partner. Said beloved partner is not only allergic to dust/dander, but he is also very uncomfortable with dogs. For the work I need done, I really can't have a breed under 30lbs. Also, although any dog I get will have daily activity for training and walks, due to space restrictions and many joint and muscle issues I cannot have a really high energy breed like a retriever or lab.
Ideally, I want an easy to train, calm and friendly breed that will have the energy to work when we're out, but will be content to relax and chill out when at home.
Due to money and time restrictions among other factors, I would be training this dog myself, hopefully with the help of some charitable trainers.

So, I'd like some advice from all you dog folks. Knowing the above restrictions, what breed(s) do you recommend I look into? Right now, Collie is at the top of my list...but there aren't many rescues up here for them. In order, my desired traits are:
Trainability / Intelligence
Low key / Gentle (no 'run up and jump on you over and over')
Can tolerate an apartment
Low dander and saliva (I don't think the hair alone sets him off)

And I don't mind discussing my disabilities with others, so if you need more information to help me out please ask. I just want this to work out best for both of us.
Thanks!