You need to find a competent electrician, whatever you do. I would request a sketch that indicates exactly what he proposes to do, and a sketch that shows the existing electrical panel and wiring, and shows any new panels/wiring/breakers. Without some type of sketch, you don't know what you are getting. Get a list of materials that he proposes to furnish and install, including panel sizes, breaker sizes, wire sizes, and receptacle sizes. Post the sketch(es) and info here. Specifically ask him how the material he proposes to install will meet arc flash requirements of the Code. I an not aware of arc flash protection available for a breaker feeding a welding outlet, so you need to resolve the question of how Code is requiring you to install something that does not exist. If the electrician cannot explain it and provide information and a written quote with a bill of materials, then find another electrician.
Here's the 2017 change to the NEC on AFCI's in the garage. It's only required on the 120v circuits. Section 210.11 (C)(4) Garage Branch Circuits Modern garages likely have lots of tools used, so now a dedicated 20 A branch circuit is required, supplying receptacle outlets only. It’s also now permissible to feed any readily accessible outdoor receptacle within range as well.
I cannot answer that one; that's between you and your insurance agent. I will simply tell you that I know of several people who've done that due to nuisance tripping issues with refrigerators/freezers/etc. and no ill became of it.
Double check the code, talking to the electrician at work he said the code does not require them for 240 v circuts and not required for circuts over 50 amps.
Ok so I sent the electrician this message: Let's see what he says. If that's the case then he explained it poorly to me the first time and it sounds straightforward.