I am curious about the first thing... urinary tract infections in rabbits are very rare... and rabbit urine being 'off'.. .what does that mean? Rabbit urine can look very different day to day and still be normal.. sometimes white and chalky, sometimes watery, sometimes yellow, sometimes clear, sometimes orange, sometimes red, sometimes in-between, sometimes with chunks in it etc.... all normal. Only way to diagnose a bladder infection in a rabbit is to get a sterile sample of urine (via a cystotomy) and grow a bacteria from it... otherwise it is not a UTI. Even blood, though rare, (real blood- most 'blood' found in rabbit urine is really a reddish porphyrn dye, which is normal or sign of stress) in urine does not mean a UTI.. just means there is something causing bleeding in the bladder (or reproductive tract if its a female)- could be a stone, a tumor, bladder trauma, etc. Either way, might want to be sure this is real infection before giving medications.
Baytril, if made from the injectable formulation, tastes horrible no matter how much Cherry syrup you add to it... even banana syrup, probably the best flavor for covering up bad flavors, cannot mask injectable baytril.. it not only tastes bad, it is chemically irritating to the mucus membranes (this is what my compounding pharmacist told me... I guess he actually tastes medications now and then). It is no wonder bunnies don't take well to this product given orally. However, saying that, it is not supposed to actually be harmful... just yukky.
Kale is indeed very high in oxylates. There are a number of websites that list the oxylate contents of greens, and though many have variations that I do not understand, most will list kale high on the list. Kale is one of the very highest- common cause of oxylate toxicity in large animals actually (not sure why any animal would eat kale.. I hate the stuff!). However, saying that, there is still much controversy over whether oxalates in greens are high enough to even be a clinical concern in rabbits. Many rabbit specialist feel they are not, but cautiously suggest not ONLY feeding these greens, and varying them. Lettuce, though not terribly nutritious, at least seems to a good alternative to give in place of kale and the others periodically. There are actually a lot of good green leafy veggies (list right about this comment shows that) that are not excessive in oxylates.