Whether or not a paper has to go through another round of reviews is up to the discretion of the editor. "Minor revision" and "major revision" are gradual, not categorical distinctions and have no guaranteed bearing on how the next round of revision must be treated.
Is your collaborator employed somewhere, at university or in industry? If so, he surely has co-workers, and their e-mail addresses and phone numbers can be found somewhere in the internet.
Try to get in touch with one of them. Call or e-mail his secretary, a postdoc, some other co-worker. At least one of them certainly knows why he does not answer and might ...
I am wondering if a call is not an option.
You can also call the reception at his/her institute, one of the students, etc. The fact that the deadline for a paper you both wanted out is approaching gives you the right to try every way to contact him, in my opinion. This would also let you know if that person has problems of a sort, though their nature might ...
(Promoted from a comment.)
As well as agreeing with other posters that you might as well start working on revisions yourself, I would strongly suggest that you contact the editor now rather than waiting for closer to the deadline. You can indicate your uncertainty, i.e. that everything might be OK (co-author responds to your queries, revisions get made, ...
I personally would start to write the revision. Maybe the person is just on vacation?
If your co-author did most of the wrting (as you said), I think it is in his/her interest to get this article published.
Basically you have these two outcomes:
Your collaborator answers before the deadline
Your collaborator doesn't answer before the deadline
So think ...
Certainly you can start on revising yourself while you continue to try to reach the other person. If you reach them you can give them what you have done and continue from there.
Perhaps you can reach them through a third party if you know of someone, perhaps someone they work with.
Doing nothing seems like the worst option.
But if you have to send in your ...