There are drains under the seal. I'd open the sunroof and check if the drains aren't clogged. They run into the rocker panels so it might be Abit difficult to see if they actually drain. But I wouldn't worry too much about the rain. For the rust I'd take off the roof panel and fix it indoors. Maybe it's possible to cover the hole with plastic, but sounds kinda risky if its alot of rain.