I am so sorry Mr. Mogli is sick!!
Did the vet determine what the problem was? Is it his kidney? The symptoms you describe (throwing up once a month, normal bloodwork then getting really sick quickly and throwing up everywhere) sound a lot like what happened to my Willy. For us it was Willy's gall bladder that was acting up. There was a mucous plug that was blocking his gall bladder. Have they checked that or ruled it out? That may not be what it is at all. I just wanted to mention it because it sounded similar.
I hope he gets well very very soon!!! My thoughts & prayers will be with you!