Blast from the past: one of my very first AH answers discussed exactly this for medieval Latin Europe!

In cases of paralysis or impaired mobility, medical texts prescribe care (treatment/hopeful cure) like applying heat, ingesting various herbs and spices, and the odd instruction to wrap the impaired limb in fox fur or breathe in vapors from the fires of purgatory. Based on modern medicine, I'd guess the first two, at least, were focused towards pain relief to some extent. I've never seen anything about help in urination, but medical texts aren't my specialty so that's not saying much.

Socially, late medieval guilds generally had statutes to provide financially for members who became disabled, due to sickness, old age, or industrial accidents like carpenters who had a house fall down on them (London 1389 for the falling house; most are more general). Poor people without familial support generally ended up begging, although some found shelter in hospitals (shelters) typically run by religious houses. Most paralyzed people probably ended up financially dependent on their families.

As far as getting around, probably the best details come from saints' lives and miracle stories. Some mobility-impaired people were able to drag themselves to shrines (in hopes of a cure) with the aid of crutches, or by crawling. Most stories involve the person being "brought" or "carried" by others--family, friends, occasionally local people they paid. Carrying might mean in a basket, on a horse, in someone's arms, on a stretcher or a litter. A few miracle stories also let us know that the person seeking the miraculous cure had help getting dressed, out of bed, etc. from family members.

I have zero clue about impact on life expectancy. A lot of the sources are concerned with impaired mobility that comes with old age, which skirts the question; the emphasis in the miracle stories is obviously on how the petitioner was eventually cured.

New to this post (heh): Irina Metzler, the foundational medieval disability studies scholar, has more recently identified in a manuscript illumination what she thinks might be a 'chair with wheels' used by a person with a mobility disability. However, there is a big difference between one artistic example and widespread use.