"as is" contract.Radon test came out high.Walk away or negotiate?

[Alberto C.]

Dear all,

I am at my 7th day of the 15 day inspection period. I signed a "buy as is" contract, in this way the seller went down 20k. They are a couple moving out of town so they are motivated to sell. The inspection found many many minor problems (like bad outlets, dangerous branches to trim, little minor cracks here and there following concrete blocks but all normal stuff, no diagonal stuff)  and 1 major problem, i.e. a couple of rotten/wet wooden beam and wooden floor plank in the crawl space, probably a few thousands dollars (2000-3000) to fix/them, no big deal. The inspector, a very well know and highly esteemed person here in town, said: "this is a very solid house for its age (sixties), I see no reason for not buying it". A couple of days after the radon test came out, with a level of 14 pCi/l. It is very high, remediation is suggested above 4 pCi/l. I read radon is the first cause of cancer for non smokers. I am a bit freaking out, and at the beginning I was really thinking to walk away. Now I am more rational, should I probably consider to ask the seller to cover the costs of radon remediation (usually by doing some work on the crawl space) and at this point also to ask fixing the rotten wood on the crawl space? I remind you that I signed an "as is" contract.
Thank you