Based on advice I measured this and that voltage, resistance and cap values, examined solder joints over and over with a magnifying glass, but just couldn't find anything off. I was even advised dude you need to ship those off to someone who knows tube gear to check them over, you obviously messed up the builds big time.
Except I hadn't. Two inexpensive add ons solved all my issues.
First was a bucker transformer. Parts cost me about 50 bucks. No more blown tubes, fuses, or red plates. I can leave the amps on now for days on end, they just glow calmly. Problem was not build quality but rather an all too common one these days, excessive utility supply voltage. The bucker lowers it to a safe value.
Second was even cheaper. Cheater plugs to float the grounds, costing a couple bucks apiece. Totally eliminated my hum issue, background is totally silent now.
These two simple add ons added up to a world of difference. Feel free to share any others.