Who spec'ed limestone for a top in a busy restaurant?!
The STT sealers are great stuff and have to be used as a kit - SB first and then the FE. You probably would need a lot more SB than FE, but a gallon would be serious overkill for your application.
No sealer, no matter how great, will change the softness of the stone or its proneness to etching, though. Those characteristics can not be sealed away.
Edit: See if you can get a hold of TYW's own Steven Hauser
. He is the chemical guru behind the STT line of sealers (and other products) and he will be able to help you with your questions.