You are apparently a rank amateur at being a landlord and you should sell the place and get out of the landlord business.
Here's why.
Amateur mistake number 1:
You should have served them a pay or quit notice the absolute minute that they failed to pay what they were supposed when they were supposed to pay it and follow up with an eviction in court when the deadline of the pay or quit notice came and went.
Amateur mistake number 2:
NEVER keep the utilities in your own name. Put it in your lease that the tenants get the accounts set up in their own name by the time they take possession and that you are taking the accounts out of your name the day before possession.
Amateur mistake number 3:
Always serve your pay or quit notice immediately the day after the day a tenant defaults on rent.
Amateur mistake number 4:
You don't OFFER to have it looked at. You say "I'll have a repairman come over today." Then you call a repairman and just get it done.
Amateur mistake number 5:
That's not their option. It's your option. You get it fixed immediately upon learning that it's not working and YOU tell them when your repairman is going to be at the house fixing it, whether they are there or not. If they don't want somebody there when they are not home, they WILL be there when you tell them when the repairman will be there., you can bet on it.
Amateur mistake number 6:
NEVER rely on a tenant to do anything to absolve you of your statutory obligations, no matter what they say.
Amateur mistake number 7:
You should have served the pay or quit notice for that the minute you discovered that they breached the lease by having the dog there.
Amateur mistake number 8:
Never take legal advice from the enemy.
Amateur mistake number 9:
Always get a security deposit of 1 1/2 months rent (at least).
As already pointed out you must mitigate your damages by rerenting as soon as reasonable possible and then they will only owe you for the interval from the move out date to the rerent date. If you don't mitigate they can use that against you in court along with claiming that the defective heater was constructive eviction.
Irrelevant with regard to your decision to sue them or not.
Although with the heater issue a judge might rule that they had good reason to move out. In case you are wondering, there is probably something in your state's landlord tenant statutes that says you can't accept a tenant's waiver of your own obligations.
You might just want to consider accepting this fiasco and consider it a life lesson from the school of hard knocks and learn from your mistakes if you plan on continuing to own the rental.
Meantime, here is the Indiana landlord tenant statute in case you haven't bothered to study it yet:
http://law.justia.com/codes/indiana/...32/article-31/

