Andrew,

Try uninstalling tablequote trough admin/build/modules/uninstall (you must "reinstall" the module files in order to see it ) this should clear some db tables and maybe any associated conditional actions.

For free shipping over a certain amount i use and recommend flatrate. Make a free shipping flat rate and enable-it using conditional actions. You can also disable global quote using conditional actions for orders over a certain amount.

I'll add 2 decimals to the weight tables. Here i use grams as weight unit so having decimals doesn't make sense i hope 2 is enough for you. MySQL returns float with 8 zero-filled decimals or so, it looks really ugly if i don't truncate it. By the way, all decimal are stored and used, rounding is only done on display.

Cheers

Joan.