Yes, it looks strange but it's spelled that way for pronunciation purposes. Here's a common expression in English, "Keeping up with the Joneses." (It refers to the compulsion we may feel when our neighbors {the Jones family} buy a new car or decorate their home with 1,000 Christmas lights and we feel compelled to do the same so as not to be outdone by them.)

Yes, I think so. My last name also ends in S, and I form the plural like that.

Yes. But it should also be pointed out that in speech we do try to avoid things that sound like an awkward double plural, even when correct. (Wilkinses doesn't sound too bad.) But, for example, if Jack Rodgers arrives with his family, I think it would be rare to hear "The Rodgerses are here." We would more likely say "The Rodgers are here." or "The Rodgers family is here." or "Members of the Rodgers family are here."