1. You need to go to the actual Google adwords tool:
try this
https://adwords.google.com/select/KeywordToolExternal
Estibot data is taken from a database snapshot. Exact numbers do change from month to month and season to season FYI
2. Names that look good "on paper" nice searches, generic, etc. can sometimes cause us to overplay (overpay) to get them. How much development and advertising could you put into a brandable KEYWORDswimwear.com for the added expense of getting the .net? How much SEO value is in the .net, can you even hope to compete in this niche?, etc? As a reseller, are you going to tie up funds and be left with a name that is tough to sell?
3. I don't have any inside knowledge on exact previous sales prices, but it failed to get a minimum bid at a previous auction, and I read somewhere that there was a 3,500 offer once made for it. No way to determine exactly what this one has changed hands for or if any of that info is legit.
If it were me and I really wanted to be in this niche, i'd keep looking for a really fun and brandable domain or a ADJECTIVEbathingsuits.com (cool,hot,etc.) type domain that was cheaper. I'd also go with the plural, not the singular. I like product domains, but I would also think twice about swim wear. Do some market research - how many people buy bathing suits online? What kind of return rate is there? I stay away from apparel, but that's just me.