Harrison,
Currently the Bootstrap content assist is not available for CSS classes. We already have an enhancement request filed to support it. We will keep you posted about the support schedule.
Regarding the custom styles and component styles not working, please share with us the exact details of the styles you are testing to help us replicate the problem at our end. If possible, please share with us the project files for further investigation.
Apologies for inconvenience caused.
–Swapna
MyEclipse Support