Firstly, as to ending the tenant early the landlord does not have to agree to this. Your only options are to assign (but a new tenant is never going to take on the fag end of a tenancy) or you let the tenancy run down. Either way you are contractually obligated to pay the rent to the landlord. If you do not pay you can be sued. You cannot assume that it is acceptable for the rent to be paid out of the deposit.
Because you still have a tenancy the landlord should not be carrying out remedial works and decorations without letting you know. There is probably a quite enjoyment clause in the agreement which prevents the landlord from accessing the property during the term, unless you are in breach but even then notice needs to be given, save in cases of emergency.
Was an inventory carried out at the start of the tenancy.? The landlord can only make fair and reasonable deductions. If the deductions from the property are unfair and unreasonable you can raise a dispute with the tenancy deposit scheme when the landlord returns only part of the deposit having made unreasonable deductions.
I hope this helps, any questions or queries ? I am happy to assist further .