I went through this in December so I can help with some of these.
- Pretty much any and everything related to a normal tenant hiring process is available to you if they still have them on file. Luckily I was in a situation just like yours and the tenant wanted to leave at the end of her lease as well so I was kind of lax in the due diligence of the tenant.
- Lease is pretty much attached to the land and not the owner so yes you have to honor it. Major ways around this is making a tenant relation a condition for the sale to the owner, or trying to buy the tenant out of their lease yourself.
- The security deposit would go to you on closing if you choose to manage yourself. I had the same thoughts you did. If I know for a fact I'm changing out floors, appliances, painting etc, it seems unnecessary/ even petty for me to hold onto a security deposit since I already accounted for those costs. As long as major damage wasn't done by them after you purchased the property.
- Yes you can see and make sure you understanding any long standing repairs or anything they've had to do with the property.
- That's fine just keep the deposit that you'll get at closing. Gotta leave some kind of incentive for them to not trash the house.
- I'd say after closing just talk to them and get any additional information about the house that the owner wouldn't tell you.
Good luck with everything! I loved buying a property with a tenant already in, even if the rent was under market. Getting paid immediately felt great.