Couple comments on your bullet points;
4; I suppose there are cases when there is no fever, but I'm thinking that a high fever is a usual symptom. It's my opinion that you'd know if he were hot, even without a thermometer.
5; Normal. neutered or not, that's just a k9 boner.
6 and especially 7 make me think that you're doing the right thing seeking treatment and ruling out blasto. But I suppose this could be part of his recovery from HW.
I'll end with an anecdote from my blasto story that closely resembles yours. Way back when, my vet too was "just doing a test to rule out some bad things". Of course, I asked what bad things? I had never heard of blasto either. I even wrote it down on a business card, so I'd get the spelling right. My vet told me, because she knew me so well, "Now, don't go home and google that, you'll only scare yourself. I'm just doing this test to rule it out, OK?"
Of course I ran right home and googled blasto. Boy did I scare myself too. Back in 2002, there weren't great sites like this, there wasn't the MV antigen test and boy, was blasto a big unknown boogeyman. Well, the more I read, and the few days ticked by, the more I realized that this is exactly what was wrong with Knight. So much so that even before the fungal titer and culture (back then they tried to culture and grow the damn thing to confirm the Dx) we got him on Sporonox and two days later the results came back.
Knighty lived through the blasto and the Itra + ampho-b therapy, although his liver enzyme numbers were always a little wonky after that.
So, you've googled blasto, wound up here and got the pants scared off ya. For you and Bear's sake, I hope this is a false alarm. One other question for ya labdad, Where are you currently located? I know you got Bear from LA, which is a potential blasto infection area, but I'm wondering if you're currently located in a known hot spot?