Trailer questions

Ok guys, taking on another project since I have some downtime.
I am gonna mount a gas powered miller welder on this trailer, because I relocated the fuel tank on the welder I can't put the batter on the welder so I'm going to mount the battery in the tongue of the trailer so I can run accessories (Backup lights, and work lights) off of it.

Now obviously I want to run 7 pin configuration because it's simple and it has everything I need and more (Brake wiring), do I need to mount a battery tender in the box with the battery and run the power from the truck to the tender? or do I just run the hot wire straight to the battery?

And another question, it currently has 7-15.00 load C tires on it, I'll be replacing them because of their age. I want to use truck tires (Load C or D) for the higher speed rating than trailer tires, and I also want to keep the aggressive old school military tire look.

From my research the biggest difference between LT and ST tires is the sidewall design, the ST sidewall is designed to be stronger than LT sidewalls under side load, however since this is a single axle trailer there won't be as much side load when turning.

It should be fine to use a correctly rated LT tire, shouldn't it?

The welder weighs ~550 and 90% or more of the weight will be on the axle, oxy/acetlene setup will weigh 70-80 lbs and will be mostly tongue weight, battery will also be on the tongue so that's another 30 (?) lbs.
Hose reels and hoses will end up being ~100lbs and also assume 2 jerry cans of gas so another 30 lbs (Not sure on mounting location).

So that's a total of approximately 775 lbs on the trailer.