1989 Bertram 50 Freshwater Tank Replacement, Soft Foredeck?

I have a 1989 Bertram 50 under contract. Mostly very well taken care of but two troubling issues arose during the survey. Issue one: the stainless freshwater tank under the cockpit floor was found to be corroded and weeping. Does anyone have any experience either trying to weld/patch these (two ugly areas) or cutting out the floor to remove/replace? There are hatches on either side of the tank for the generators but no good access to the tank itself. Issue two: the port bow has a large soft spot where d-rings were attached to the deck to secure the crane arm. My assumption is these screws worked loose and allowed water intrusion. The area is inboard and above the walkway/toe-guard and starts at about 3 1/2' width and tapers forward to zero. The core appears to be gone. Seller is amenable to a credit for the repairs so I am looking for budget numbers.
The boat is in San Pedro, CA. If we can agree on a credit and sale my plan is to move it to the San Diego area.
Thanks in advance for any input.

Apologies, failed to state length of foredeck soft area. At the rear is 3 1/2' across extends forward about 6' tapering to zero, like a piece of pie. Thanks.