The swap size ought to be OK; the root size, however, you need to think about.
If you're going to add software packages (such as OpenOffice/LibreOffice, VirtualBox) they install by default in /opt (which is part of your root partition) and many applications install in /usr (also part of your root partition). Then, of course, your might want to do some data base work?
You might want to either increase root to, oh, 25G, maybe 30G or 50G or add some other partitions for /opt, MySQL or PostgreSQL, and the like depending upon what you anticipate your needs to be; 25G, 30G or 50G out of 800G isn't wasteful -- your logs, additional applications and other software all will install in the root partition and you'll need some space. It's hard to estimate how much you'll need but there is the "off you can take, on you can't put" rule to consider. And do you really think you'll have 750G or so of stuff in your home directory, eh?
On my own systems I allocate 15G for the root partition and I have separate partitions for opt, psql (PostgreSQL), mysql (MySQL), /usr/local, virtual (VirtualBox virtual machines). If you install, say, Win7 as a virtual machine, you're going need at least 20G just so you can use the blasted thing. My root partition includes /usr, /var/logs and other base system directories and is 57% used.
You really do need to sit down and think about what you're going to want to do, how big it's going to be and where you're going to put it.
Booting from the MBR is fine, booting from the root is fine (I lean toward MBR).
Hope this helps some.