1. The amount of installed modules does not affect game performance.
2. You just move the installation folder to the SSD drive
3. Get 256 GB (thrust me on this ;)
It would be nice if you have your specs in the signature (15 or 25 fps is like slideshow to me)
Let me know if you need more help to set DCS to perform more fps ;)
Take care,
Piotr.