1. are there any rules which forbid a monk from eating at a restaurant?
No there are rules about eating at a communal food distribution place (name?) but these would not be an issue here.
2. are there any rules which forbid a monk and layman from eating at the same table ( but not sharing food) ?
no, obviously there are rules about things being properly offered and as long as that is kept then there should be no problem. but ask the monks/transport co-ordinator for clarification on popper protocol.
He who knows only his own side of the case knows little of that. His reasons may be good, and no one may have been able to refute them.
But if he is equally unable to refute the reasons on the opposite side, if he does not so much as know what they are, he has no ground for preferring either opinion …
He must be able to hear them from persons who actually believe them … he must know them in their most plausible and persuasive form.