Yasurime are yasurime. I do own a sword with gyaku takanoha which is pretty rare but it leaves me cold; having said that, as it's a suriage and mumei blade, it helped me find the blacksmith.
This is one element, but the tsuba is also used to protect against the opponent's blade, which is why it's made of soft metal so it doesn't break. In Katori Shinto ryu, there are several techniques using tsuba.
Most likely. They are minor smiths, so there are no examples of their work in the literature, which makes a declaration of gimei hazardous. That's not to say it's not a gimei, only a shinza shipment will tell, but is it worth it?
越前住宗次 Echizen (no) ju Munetsugu. According to the literature, there are 2 generations working in Kanei (1624/1644) for the shodai, and Kanbun (1661/1673) for the nidai.