I'll assume your "potlights" are ultra-slim LED can lights?

An LED driver is the power supply that outputs the necessary power for the LEDs. The j-box would be the metal box where the electrical connection is made.

The webbing on a TJI is the OSB between the upper and lower chords. Just be sure to follow proper spacing and sizing when drilling through the joists.

Rather than just setting the included j-box on the plywood, secure it to the top of the plywood.

How are you planning to run your Romex? Drilling through the webbing of your TJIs? Stapling Romex to the bottom of joists is only code compliant (at least in the US) if there is backing, meaning you can go along one joist, but can't go from joist to joist to joist.

334.15 Exposed Work.

(C) In Unfinished Basements and Crawl Spaces. Where cable is run at angles with joists in unfinished basements and crawl spaces, it shall be permissible to secure cables not smaller than two 6 AWG or three 8 AWG conductors directly to the lower edges of the joists. Smaller cables shall be run either through bored holes in joists or on running boards. Nonmetallic-sheathed cable installed on the wall of an unfinished basement shall be permitted to be installed in a listed conduit or tubing or shall be protected in accordance with 300.4.

>5 nights out of 7

Anyone who's been on reddit a while will know that 5/7 is a perfect score. So, can't complain.

/u/PioneerStandard's answer is partially correct, but not fully correct. While these bulges do occur because the drywall is not fully flush to the support behind it, bulges this big are usually because of either a foreign object (insulation, staple, etc.) rather than a drywall screw not fully seated. This also often occurs when the top plates sit back a bit from the studs.

A proper fix is to cut out the bulged area, remove all the loose material and mud over it. Answers that suggest hitting the area with a block/hammer, while may appear to work, only serve to break up the gypsum between the layers of paper. It may work, but it's not an actual fix.

I don't usually vote and I'm not a fan of dogs. But I gave you an upvote because your message is a good one.

Not sure where you are but here in the US, water heaters usually max out at 60°C (140°F) as that can already cause serious burns after a couple seconds. I'd be seriously suspect if your tankless is putting out the temps you claim. As for sanitizing dishes, your dishwasher will heat the already hot water to the necessary temps.

Your temp should be regulated at the heater, not the bidet.

What angle are you cutting the material at with your grinder? You should be as close to a 90° as possible to minimize the cross section at your cut. Trying to cut much longer areas will cause your problem where cuts seem to take forever.