1. If its not leaking leave it.
2. If you don't like the look, make a perspex blade and slice the excess off.. (A perspex blade is a bit of perspex with sharpened edge and shouldn't score the wall, don't use steel or alloy, some kitchen spatulas trimmed will work as well......DiY)
3. To do it properly you need to take the door off, remove screws then run a plastic blade around the seal to loosen it, clean the old sealant and foam off with turps and a plastic scraper, then run a new foam strip followed by a run of silastic/mastic and refit door..... do the screws up like wheel nuts, opposite's and not tight all at once, work around a few times , they don't need to be super tight or the door will distort.
4, I would go for 1 or 2 myself...... unless its leaking..... the mastic type goop does crinkle and crack but still has integrity... you may find its a mix of goop and foam seal.