Typical roof-mounted A/C gaskets won't repair a roof tear. The gasket needs a firm support without any way for water to get under it. Eternabond tape would be my choice for roof repair and I'd investigate the possibility of a small 5K BTU window unit. A small window A/C will freeze you enough and may be easily portable for seasonal use. I have a window A/C unit mounted in my tent camper and it gets it cold enough to hang meat, even at 90f with 85% RH. The kids complain about the cold at night so I get up and turn it off in the middle of the night. By daybreak, the interior is back to ambient.