Feline Vasculitis and next steps

Species: feline

Age: 1 year, 4 months

Sex/Neuter status: male

Breed: mixed tabby

Body weight: healthy

History: Perfectly healthy cat when we got him in December 2015. Missed his last round of kitten shots due to rescheduled appointments and vet closing, got them in Sept or Oct 2015. Went on a honeymoon and left the cat with parents. Picked him up and he was fine, next day his ear was bleeding and we assumed he itched it, then he expressed pain in his paws when picking him up and limped when I set food down. Brought him to ER, diagnosed with vasculitis. Unrelated, in early January the poor guy had a urinary blockage and was sedated and on a catheter. Weaned off prednisolone and the medicine to relax urinary muscles. No other flare ups. Jan 22nd ish his ear bled again, got him to the vet and now back on prednisolone and another medicine for vasculitis. No new news but still on meds and now less friendly in the morning and at night when he typically receives his medicine, hiding under couch a bit more but also has days of extreme affection.

Clinical signs: Presently nothing beyond hiding under couch more often BUT he was never a "hider" before. Continues being affectionate. Looking more for signs on what vasculitis actually is.

Duration: 3 months, ish

Your general location: Northern CO

Okay, in addition to all of the above, we took our honeymoon in Mexico where we did pet a stray cat. I'm terrified something got on us and we brought it back, but I interacted with my parents cats upon picking my furbaby up from them and they did not get ill at all. No contact with any other cats (neither on my behalf or the cat's) after it seemed his vasculitis was healed the first time. (First time was around Dec 4, then we weaned him off his meds in early Jan, then by Jan 23rd ish, vasculitis symptom returned in ear).

I guess I'm mostly wondering what vasculitis is in cats, what I can do to help my little guy and what the prognosis is. I've brought him to the animal hospital a few times and no one has indicated what the prognosis is. I also just wondered if someone would speak to him starting to hide more and hopefully be able to reassure me that it isn't anything serious. He hates having pills shoved down his throat (shocker) so I'm guessing that he just wants to be less available, but these moods come in swings. Yesterday he hid under the couch all night, today he's been a cuddle monster.