I think I gave you my answer to most of those questions on thingiverse so I will let anyone else chime in. I’m not trying to be difficult or unclear with my answers or the website, but some of your questions are tough to answer and are pretty subjective. I try my best to break it down here, http://www.vicious1.com/specifications/, but let me try again in a nutshell. This is a super generic non specific cnc platform. Nothing is locked in, any software (slicing, CAM, laser, ect), any hardware (steppers, controller, drivers), any size (within reason, keep the z as short as possible for best results), any function (laser, vinyl, print, plot, mill). That is why the answers seem vague to you, I think.
Your shopping list looks right, if you add in some filament from somewhere else. We already talked about the resolution, but I don’t think many people print at .1mm on this machine most are going for larger faster prints with larger nozzles. Small print volume machines are common, large ones for this price are not.
Switching tools with the stock mounts is a few screws, but some of the user here have gotten together and made a hell of a quick change system that makes this even easier. No re-calibration really just reset the z, but I do that with every print, as I don’t use/recommend end stops unless you are only printing then what ever floats your boat. My DW660 mount does not have a hose attachment, but there are some that do. The hose can cause a lot of drag on the machine so please be careful of how it is attached.
Ramps is arduino based. my customized marlin is pre-flashed on the boards, and it is available for download on the marlin page, or you can do it yourself, or you can use any other control board you want.
There are plenty of 3D print packages out there, more for PC than MAC. Have a look at Slic3r, matter control, repetier host, cura, craftware, simplify 3d (paid).
So the downside…This is very, get your hands dirty. You will be building it by hand. Monoprice’s printers come pretty much ready to go out of the box, this does not.
Side note, I had one of the monoprice printers and it had 2 issues, I had been talking with one of there execs about something else and told him about 2 major issues it had and I sent mine back as well. What was the problem with yours?