Pay for a inclusion at a high pagerank directory is probably the fastest way...
I've got from PR0 to PR5 in 2 months.
My comments on your suggestion above:
1. Spammy. SEs might consider your site spam as you generate too many link in a short time
2. Could work but gathers more traffic than PR
3. Great long term strategy to build PR
4. No.. No.. No.. Reason as in no. 1.