Not, there is very little Rust in the kernel. It’s still WIP and there no real world Rust drivers in the mainline repo yet. It will probably change “soon”, but even then Linux will remain 99% C for the foreseeable future. You can’t just rewrite something like that in Rust.
That’s also true, but I have experienced an occasional issues when it would be stuck on downloading some package at 10 KiB/s because of bad mirror. Parallel downloads likely wouldn’t have helped in this case since it would select the same mirror. Obviously both issues need to be fixed though.