Invitation for campus visit for post doc position - salary negotiatons?
It is certainly fine to ask for clarification of what you were told about the salary and other financial details.  Keep in mind that nothing is certain until you have an offer in writing.

See How to handle salary negotiations while negotiating a postdoc position? regarding negotiation of postdoc salaries.  My guess is that the salary would be negotiable only within a narrow band, if at all.  If you get offered the tenure-track job, you shouldn't expect the postdoc employer to try to match it.

The main reason to choose the postdoc over the tenure-track job is if you think that the additional years of full-time research will help you get a better job afterwards, or improve your research success over the long run, and if you think this will compensate you for a couple years of a lower salary.  It very well might.

Keep in mind that a position that "focuses on teaching" will likely have teaching loads that leave you very little time or energy for research, and may also not give you much funding for that research.  I think people who take teaching-oriented positions very often overestimate the amount of research they will actually be able to get done.