When using the phrase "two towns over", how many towns are in between the locations in question?
Solution 1:
Merriam-Webster gives the relevant sense:
over [postposition] on the other side of {an intervening space, location etc}
- the next town over
(POS adjusted [compare beyond the next town, where 'beyond' is obviously a preposition] and otherwise slightly adjusted)
So 'two towns over', though it sounds rather unidiomatic, would be 'beyond the next town but one'.