[markbolyard]

On shared hosting, I think you are going to be out of luck (But, in my experience you should be able to ask your host to create the mysql database for you, and place it in a non public place for you to download it. When you create your local copy of your site, most likely you won't be able to restore that database without timing out, so search google for something called bigdump. It's a script that can restore your database by spreading the dump out over time or by chunks (Read their site about it... I might not be explaining it too well).

You most likely will need to get on a more stable hosting plan... a vps would most likely be minimal...

When you prune, just try and figure a way to do it in blocks, or chunks... DON'T run any sql commands that would delete post, or you will mess up your database and won't recover it. Get that host to create a backup, download it, and make a copy so you aren't working with the only full backup you have. Hope these suggestions help.