In regard to your domain, that will continue to be registered to you. In fact, the $9.95 annual domain registration fee isn't actually refunded to you - just the rest of whatever you paid.
You can either keep the domain registered here and point NFS to your new host or you can transfer the registration over to them too.
As digitalvibe has said, 90% is terrible and if I thought that's what I'd have to live with, I'd be switching as well. It's bound to be a bad neighbor so you can try reporting it when it happens (they're really interested in finding out as much as they can about these slowdowns, since they affect everyone on your server).
What are [color=#CC0000]50DISK50[/color], [color=#CC0000]3DOM50[/color], and [color=#CC0000]1IP1DOM50[/color]?
They're Dreamhost coupons!