As long as you have persistant connection off - then you're fine. Again the slowness and database corruption may be the result of someone else on the server.
A crappy and or unreliable MySQL server is something you'll have to address with your web host. Data can get corrupted if it can't handle the load.
The lag you've had may not even be your fault. Again, you might be sharing that server with 100+ more sites. Ya just never know.