That jamb needs a bunch of work before worrying about that seal.
It was shimmed wrong and the jamb may be twisted causing all the gouges on the latch plate.
It needs to be sanded to get rid of all the dents, gouges and scraped off paint.
Primed and repainted two coats.
Any place selling Masonite doors should have that weather sealing stock.
Just grab ahold of it at the bottom with a pair of pliers and pull it out.
Any box store will have a weather stripping that's an aluminum strip with a bulb of white rubber seal on it that gets screwed to the jambs in elongated slots that will work better to seal it.
MD Building Products
Top and Side Door Jamb Weatherstrip Set
Model # 01958