This is the reason why I love teck90 so much. Sometimes im too lazy or don't have time to bury conduit, and I won't buy garbage. Leaves teck as the answer
It takes time for the conductor to burn once damaged, but sometimes not long.
I've pulled out burnt wires after 20years,
Your electrician will megger the cable to test insulation, I always to this to motors before calling it bad
It could be something different, sometimes it's hard to...
I would pull solid wire because I'm not sure what devices it's going to be connected to but it's a lot easier to terminate properly on a setscrew then stranded wire which technically isn't supposed to be terminated by wrapping around I setscrew
Just plug them in, a bit of dust will be removed from the contact points from the friction of plugging it in.
A concern is metallic brake dust which accumulates in panel in certain situations. - conductive dust
I have a similar heater, 45k schwank...
Mine had similar specs, even @ 6" the ceiling gets hot (I can still hold my hand on it without discomfort) but everything is 5/8 type x so I'm not concerned.
If I were you I'd build a shield, even just a strip of concrete board with an airgap between...
My shop is to clean to work in, basically a man cave. Has a smart tv, a minisplit, wifi thermostat, etc. I do odd projects In there but I'm a neat freak so it's natural to keep things in order.
For major things I go to my business shop/warehouse.
Why are you using seal tight? That's terrible stuff to pull through and I mean terrible. You'd be better off buying direct burial cat5e. Then sleeve it with pvc when it comes above grade. If you need flexable use coreline before sealtight,
You won't push a fish tape through even 100' of...
We use 6mil poly on the warm side up here.
I'd advise to pull down your drywall, and do closed cell spray foam, and then board with type x 5/8 firecode, airtight taping on the drywall.
Due to having living space above and beside, best way to keep it safe if your using your garage for more...