A couple of maintenance questions

[Corelogik]

I was recently shut down by my host for excessive slow MySQL queries. In working with my host, and tweaking things I've gotten my sites back up, but in looking through the database, Ive noticed a few tables with thousands of records, some with over a million. I need to know if it would be safe to empty some of these tables in the interest of shrinking my 280MB database.

log_actions
log_activity
log_boards
log_mark_read
log_notify
log_polls
log_search_results
log_search_subjects
log_topics (My biggest table, 1,721,623 records)

Second question, is there a way to completely remove old topics while retaining members post counts?

[a10]

Similar questions, no replies at the time.

[Corelogik]

Thanks for the link to the other thread, I tried looking for related posts to mine, but couldn't find one. Ill be keeping an eye on both threads.