2003 Dodge Ram idling rough misfiring low revs high revs fi

I have a dodge ram hemi 1500 quad cab which ran fine until a particular cold spell which may be coincidence but it was out of action for a week due to snow, pipes were frozen so defrosted with hot water, it did have antifreeze in it but not enough as it was our bad freeze we had in dec/jan afterwhich the car ran fine for a couple of weeks then started to run rough for a few weeks then ran really rough within a matter of days and I was unable to go anywhere, struggling idleing. Had plugs and leads replaced and diagnostics test at dodge of which they said it had low compression on piston 2, but seemed unconfident with this. A friend who is a mechanic said he thought it had various misfires and wasnt happy with the diagnosis, sadly he hasnt the time or tools to do the job. Started it again today and its making a strange squealing noise when I steer like its struggling for power, a sort of pinking noise, it runs fine when you put your foot down, its making a popping noise otherwise, on low revs, and eventually stalls, I am unable to use the vehicle
im at my wits end as no one seems to be able to tell me whats the matter and dodge have said they want 1250 plus vat to replace the exhaust valve but wont guarantee this is the problem, I desperately need advice before I get stung. Any tips