Ask you vet why he continually gave the cat steriods (depo no less) to further deplete his immune system and then follows up with interferon to boast it? This is crazy, slap dash prescribing that will have long lasting and I fear devastating effects in your cat! Its crazy to treat an initial URI with steriods (dangerous, if he had a fever). The wheezing was probably (and xray suggests) pnemonia (probably developed from clamydia infection) that could have been treated allopathically with generally specific antibiotics (tetracycline or baytril/Orbax) not steriods (totally inappropriate!). Now everything is all snowballed together, its tough to say what the heck is going on.

You need to make a very impostant choice here. Either keep on going the allopathic route OR attempt homeopathic treatment, you can not do both. The first thing I would suggest it total detox, so the true symptoms can actually manifest (right now they are probably suppressed and so there would be nothing to prescribe upon or you would be guessing at symptoms).

Whatever you do, don't allow any more depo shots, those shots very often kill cats after a year of monthly shots. I've seen cancer, liver failure and diabetis to renal failure; result from these dangerous regimes (what really annoys me is that the treatments are continued even though they clearly are not helping the situation at all!!!)