I've Got a few Landlord Questions For a Pro! :)

[Mark David]

I have a tenant in LA who has been there only about 7 years (although it looks like they've lived there for 20). I do what I can. I keep the rent $400 below market, too. The house is 60 years old. On top of that, the tenants don't take care of the place- the place is a total mess.
 

The house "shifts" with the ground and therefore, the paint peels, floors move and crack slightly, doors stick and other things that cannot be controlled. Because of the way they live, the entire house would need to be redone upon their move-out...but, unfortunately, they aren't planning on moving out. They are always wanting me to upgrade or fix everything while they are living there. For example: 1)they want me to dig out all the flooring in the kitchen and replace it. 2) They want me to dig out the old tub (because it is starting to chip) and replace it. 3) They want me to dig out the flooring and tile in the bathroom and replace it. 4) They want me to repaint the interior. On top of THAT, they want me to put them up in a hotel while I fix all of these things. As you can see, these are major projects that would take at least 3-4 weeks.  

1) What should I do? What would a PRO do in my situation?

2) Also, I am under the impression that as a landlord, I am not responsible for the normal critters (ants) that live on the property. Correct?

3) They've never complained til now, but am I required to install a deadbolt on every entrance to the house? 

Thank you in advance!