Making a Counteroffer After a Home Inspection

[Tom Server]

I'm in the middle of purchasing a older property. Its a duplex with a detached 3 car garage with an apartment on top.. so 3 doors... 

The home is 102 years old. Seller was selling it for 290k, He settled for 250k.

I just had my home inspection completed, The 2 inspectors said the home wasn't in that bad of shape for what it is. "its a 100 year home, rental property, its going to have some wear"  

Im trying to figure out how much of a seller credit or have repairs done. Some major items do need to be repaired so I'm estimating the costs.

Major items

2 Roofs- $20,000

Boiler -$15,000

Termite damage- treatment $3500

Plumbing leaks- $2000 ?

wrong door/fire proof door- $500

oil tank rusting/ inspect and paint -  ?

rotted wood thru out the exterior -?

Whats a realistic credit should I ask for ?