3kg isn’t a lot but losing that much within a single month is somewhat dangerous and generally not recommended if you have gout. Obviously I’m talking about your average weight as you might occasionally get variations about as large as 3kg simply from random changes in the amount of water in your system and so forth.
Your body would probably get used to the drug but that doesn’t mean you can’t quit. Your body would also get used to being off the drug after a while. What it means is that, unless your uric acid wasn’t very high to begin, you shouldn’t stop it without having a decent monitoring plan (such as unusually frequent blood test at your doctor’s office). I don’t know that there are studies about stopping febuxostat (it’s a less common drug) but its main effect is the same as allopurinol’s and people have been able to discontinue allopurinol for extended periods (many years in some cases).
Allopurinol stays in your system longer than febuxostat which is one of the reasons I would consider low-dose allopurinol more dangerous than low-dose febuxostat. But keep in mind that your wheezing may not be related to allopurinol.
There is a correlation between the time you’ve had untreated gout before successful UA-lowering treatment and the time it takes for the treatment to clear your crystals. So getting clean might take much less than a year in your case.
I would still keep taking the drug for a little while after the crystals are gone (see above for the role of the immune system in crystal formation).