Simple SVG Manipulation for CNC -- 2

I have a simple SVG file that needs worked on for a working.

It is an odd window casing that I am making. I traced the window outline with points, the arch needs to be changed from straight line curve to and actual curve

im making casing. it needs to be 3 1/2 wide all around the window. exept the bottom. The inside of the casing (the file) needs to be 1/4 bigger all the way around than the file. the file is a trace of the window jamb and needs a 1/4 reveal

There needs to be a 1/4 reveal and then it needs to be 3 1/2" wide trim (except for the bottom).

I am looking at a tight timeline of right now lol