Not really sure how to help you here.
1) You can usually get a riscv64-gcc cross-compiler directly from most linux distros. If you provide the distro you are using, I can probably point it out.
3) No arguments that gcc is bloated, but it is also a C++ compiler and has a ton of features.
Have you gotten any tests to work in an emulator? Starting with an FPGA sounds like a recipe for hidden bugs to me.
Thanks,
-Sam
Soli Deo Gloria