I'd think two stitches in the foundation row only...but now that ya mention it...how about 1 st at the corner of every round? The succeeding rows get bigger around as you go...so I can appreciate your question! I'd tinker with it.
[COLOR=Blue]Great looking blanket! And the yarn will be so soft, and classy, at the same time! Wow! What a wonderful project!
As for the border: whereas I haven't read everyone else's suggestions, I did read someone's idea for applied I-cord. That would be great!
And, then how about CRAB STITCH? I bordered my Sausalito Jacket with the crab stitch, and I love it! Quick and easy to do, too!