The situation is ambiguous. On the one hand, you have on hand the confirmation of payment for the hotel, and at the entrance there should be no questions, because you are going to a certain hotel for a certain period. On the other hand, the tour operator, responsible for your "safety" during the trip, is absent and the visit is private, not in the group of tourists.

I advise you, in order to avoid misunderstandings, to apply to the Consular Section of the Tunisian Embassy in Moscow at (495) 691-28-58. Perhaps, they will advise to issue a visa.