Nothing like jumping in with both feet! They are relatively complex tools, and you’ve made a model that’s particularly hard to machine.
All of the things you ask about above depend a lot on the tool. From the model you’ve made, it’s actually very hard to machine and get a result you’ll be happy with with a single tool, which means multiple tools (at a minimum). Remember, the end of a square endmill is…um…square. Without very small stepovers (that will also wear out that kind of tool on this kind of cut pretty quickly) you’ll get large steps in the angled faces. They’re great for a “roughing” pass to get most of the material out of the way. Then follow that up with a ball endmill, and use that for the angled faces. You’ll still get some stepping, but less, and it will be more “wavy” than stair-stepped. You’ll still need a touch of finish sanding when you’re done. I’d start with a .25" square tool to rough out the majority of the waste stock, then follow up with a ball end mill, and maybe follow that up with a tapered andmill with a smaller stepover. That would be a 3d “pocket” path, with maybe a .125 stepdown, and .125 stepiover. Follow that with a round endmill, ⅛", and a .065 stepover (and stepdown), and see how it looks. then might try a smaller stepover and see if the result looks ok to you - expect some wanyness in the surfaces, but see how it looks to you. Follow all that up with a ⅛ outside contour. You’ll want to export all those paths as single files, and after each one, change the tool to prepare for the next, run that, and move along like that. Using carbide motion as a sender is a good place to start. Use the feed/speed from the carbide chart (find it in the documentation on the website) - it’ll be conservative, but it’s a fine place to start.
It’s all a learning experience. You’ll pretty rapidly find the adjustments that make sense, what you can speed up, and what you can’t.
There are some things that are really easy on an additive machine (like a 3d printer) that are more difficult on a subtractive machine (like a 3 axis mill) - and they both get different results… sometimes something that’s trivial with an additive machine is just plain impossible to do in one piece on a 3 axis mill (like a hollow sphere!). Faceted surfaces are one of those things. It’s not that you can’t o faceted surfaces, it just requires more thinking things through and knowing what the machine will accomplish on it’s own. That all comes with experience. 2.5d stuff is fairly easy on a 3 axis mill, it might be a better place to start, I’d hate to see you get really frustrated trying to get good results on this particular model as your first foray.
Cutrocket has a number of projects that you might want to try first, just to become familiar with all the processes. Maybe something like this: https://cutrocket.com/p/5adf9542c9d81/ , or maybe this: https://cutrocket.com/p/5a8da9daede24/ . I don’t want to discourage you from trying some cool projects, but you might be taking on something a little more that you think you are.
Again, don’t let me discourage you!