I hate the ammonia spikes - our little Angel just had one in her tank of .5 and Sora's tank went to .25 on this week's test and they both have totally clean tanks. I've been using AmQuel+ from Kordon (
www.novalek.com) and it has worked for us. We get it at Petco, where do you get the stuff you use for ammonia spikes? We're always looking for better solutions and I'd like to compare the products and see what works best in our tanks here.
Also our 2 male bettas have those same kind of lumps on them down near the tail, our lost male Betta also always had that. From what I found online, looking at a cross section of a male betta - i think that's how far the swim bladder extends and the lumps seems to be a common thing, but I guess not all bettas have the same size swim bladder.
Have you tried a pea treatment lately for his swim bladder? I have successfully treated Platy fry with swim bladder problems so they could only move around the bottom on their side with a pea treatment. Usually what we do for our bettas is take a frozen pea and thaw it in the microwave for about a minute, remove the peel and it'll split in half and we feed each betta a half pea. Since Lava's having trouble swimming down, I guess you could try holding it so he could nibble on each half pea until you figure he's had about 1 pea's worth (your discretion exactly how much) - his eating habits sound like it won't be a problem getting a bunch of pea into his hungry mouth.
Good luck & I hope Lava will be swimming around like usual soon.