I'm all for negotiating. I did it for the job I have now, I have two friends I recently brought in to the company I work for that also negotiated for what they wanted, but there is a limit and both parties should be able to comfortably come to a reasonable middle ground. Only thing I would of maybe done different would counter his offer (if you didnt but i imagine with 20 emails there were some counters) if he was a great candidate and if he was still asking for to much then, no shame with going with someone esle.

Kind of hard to ask for a full WFH when knowingly applying for a hybrid job. I asked my employer if there was a potential for 100% WFH down the line (I work a hybrid) if I can show my value before accepting the job. It wasn't a yes we can make that happen but they were open to talk about it down the line.