You can stay until the end of the term stated in the lease, but only if you keep making the payments. I suggest you do all you can to memorialize that you made the payments. Don't rely on your landlord's good faith.
Write your landlord a letter (keep a copy) denying there are drugs in the house, asking him for the basis of his charges, and telling him you're not moving out because of baseless charges. If he continues to pursue the matter, get a lawyer.
As to the collection agency, there are protections available to you under the Fair Debt Collection Practices Act. As to the landlord, there are a number of questions to be answered re the move-in inspection, the move-out inspection, whether you took photos, whether they did, whether they gave you the proper 14 day notice, and others. See a lawyer.
Mr Corrigan is from New York, but his answer applies for the most part here in Arizona, too. The existence or not of the guaranty clause, whether signed or not, has no bearing on your liability as principal signer on the lease. If you breach, you breach.