There are known issues playing large files, such as this, from the touchscreen. I think I remember hearing a recommendation not to exceed 100MB.
Personally, I would be playing this using the Simplify3D machine control interface via USB, which has proven very stable. There probably are other options, but I don’t know any free ones off the top of my head.
Discussion on some of your questions:
Technically, yes. There’s a couple write ups. It’s not trivial. Requires manually editing a copy of the gcode file so the machine starts in the right place with the right state. Here’s one I did: Air Print Recovery - A Success Story
Yes, don’t see any reason it couldn’t. However, it’s very very difficult to print on any printer. This would probably be easiest with 2 extruders and PVA supports that are dissolvable.
You might have better luck with tree supports. It looks like your infill density is no more than 5%, try bumping that up to 30%. Will help ensure surfaces are flat.
I’d probably start by slicing only a few parts at first, like just the top gun and printing that. Make sure that’s printable. Then the side nozzles, make sure that prints.