From what you say i imagine you as an hardcore woodworker .

Let me break some illusions:

-the best Festool router is crap compared to the cheapest Chinese water cooled spindle. Once you run a proper spindle you will wonder why you ever considered a router.

-Wooden machine base is asking for problems and wasted money

-Aluminum profile gantry on that span is asking for problems. That can be cured by bolting steel back plate to reinforce the aluminum profiles though. Profiles, not profile.
There is a cheap way to make a steel gantry and more expensive way, to make aluminum plate gantry. On your intended span the gantry will be somewhere like 1450-1500 wide/for 1000mm travel/ . So you don't need to know how to solder. Just design it and have somebody made it for you. It will still cost cheaper than aluminum. And the aluminum also needs to be bought and machined. So it could be as simple as soldering 2x 100x100x3mm together

-in my signature is the link to my 1rst build. You could find it quit inspiring if you like that style of machine. Somewhere inside are the free plans in sketchup. You could use ball screws, mounts and so, as i have drawn them one by one checking against the real product.
In fact all your questions about PR, ball screws, Breakout boards, motors and so are answered there. I am glad that at the time Dean broke my illusion about the rack and pinion and i ended using ball screws

-I say it every time : until you have them in your hands, dont drill holes for spindle mounts, ball screw nut housings and whatever Chinese thing from aluminum, cause many times they look the same but come with different holes placement or if they are cast the holes are misplaced some times.

I wish you luck with the build!