Move on. Way to much labor involved to fix a unibody car like a 1145 correctly, and not doing it correctly is just a waste of money.

Budget in for a trip to a part of the country where the cars don't rust, and get a solid car.

I want my Volvo's to last a long time, so I don't drive them in the winter when they have salt out on the roads. I have a 'winter beater' that takes that abuse. For years it was an old '89 Ford Bronco II, worth about $500. This last winter it finally developed a hard to fix problem (leaking slave cylinder, which is inside the bellhousing thankyouverymuch Ford) and the rust finally started to make the body fall apart in the back section, so I replaced it with a '97 Explorer Sport that cost me $1000. Cheaper rust protection can't be found, IMO.
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'63 PV544 rat rod, '93 Classic #1141 245 +t