You need to develop superior powers of observation and personal alertness. The most dangerous thing for you is to fail to be aware - to fail to be one step ahead of the other guy.
('Orange' should become your favorite color!)
Proximity to your body becomes a liability; and, one of the first weapons an attacker will use against you is your own personal instability and lack of balance. Simply put: You can no longer afford to let the other guy get that close to you. With crutches (or a cane) in hand, you are going to be, 'preoccupied'; and all forms of preoccupation are primary target identifiers!
Someone who becomes unexpectedly handicapped soon discovers that life has - just as suddenly - changed in many subtle ways. What used to be normal reaction time and distance for you is now, at least, doubled.
If the attack is definitely on and coming in, you've got to be able to let go of your crutches, get your back against something solid, and (maybe) do some good floor shooting just like that Cruise guy did in, 'Collateral'. Trying to remain standing on your feet ('like a man') is a disadvantage; and, it is an especial disadvantage against multiple assailants, too.
Instead: Teach yourself how to fall backwards along one side of your body. Don't try to fall straight back; that's going to hurt! Rather learn how to fold one knee or the other and, 'roll' down and backwards along the edge of your body. Get down, get comfortable, and guard your back.
Personally, I have found nothing faster than a good shoulder rig; just remember that you need to use a tie-down to your belt on both sides. In your present situation, I'd recommend a reasonably priced Galco or Gould and Goodrich shoulder holster as your best carry option.
Use your head: Stay out of bad neighborhoods and don't go out at night anymore than you really have to. Try to move around with others and avoid solo adventures whenever possible. The facts that pepper spray or a TASER might be effective weapons for normal healthy people are non-sequiturs.
You are handicapped; and, the sooner you learn how to effectively live with this reality, the better! So what if pepper spray is like hot sauce to many of the wrong people? So what if TASERS don't work all of the time? The important point you have to recognize is that any attempted use of these devices violates the paramount requirement for you to be able to keep an attacker as far away from your body as possible. If an attacker is already within 20 or 25 feet of you - YOU'RE SCREWED!
A normal healthy person is barely able to successfully handle a physical attack from such close range. Unless the other guy either trips or otherwise hesitates, you positively will not be! On the other hand, in spite of your handicap, giving yourself a little additional time or distance might very well save you; and, no matter what, 3 or 4 rounds of 45 acp always works - Just put 'um COM between the head and pelvic girdle!
Your own everyday personal attitude has a lot to do with the extent to which others perceive how vulnerable you are to successful attack. Being a little bit more alert, being one step ahead of the other guy, and being completely ready and willing to commit yourself to whatever has to be done is - I am certain - the best way to dissuade any thug from, either, initiating or following through with an attack.
One of the most useful self-defense techniques I know of - and one I've actually seen save a couple of lives - is a ready willingness to forcefully command; 'STOP!' 'DON'T COME ANY CLOSER!' 'I'M AFRAID OF YOU!' 'I'VE GOT A GUN; AND, I KNOW HOW TO USE IT!' 'GO AWAY!' 'GO AWAY, NOW!'
(I don't believe there's a police officer on the planet who would fault a handicapped person from the early display of a firearm. I really don't!)
It, also, helps to practice a lot and be a very good - albeit one legged - combat pistol marksman! In my experience, you're only a potential victim until the moment that they either hear your voice or look directly into your eyes. No matter how badly you limp, or how much trouble you may have getting around, that's when the men quickly get separated from the boys!
Oh, yeah, if you've got a large dog that helps, too!