I appreciate your impulse to make the guest "whole" in their experience in your home. I would imagine that dealing with all the different issues did eat into their holiday time and I think a 50% refund for the entire stay is warranted, in addition to the other extra's you have provided.
If you are getting out of the rental, short or long term, that is one thing but if you are going to continue to be a host or even a landlord, perhaps an inspection is warranted. When you use a second home for your own benefit, like most owners, you probably wait until something fails before you do anything. When you are allowing others in the home, you might need a more proactive system of anticipating problems.
I had a septic tank fail while I had guests, but I never even knew I had a septic tank! The previous owner failed to disclose it. 😛 Anyway my guests were super and never really inconvenienced, but I still gave them a refund for a day.