How to find an appropriate sex partner for a sakadagami? Is it true that sakadagami can have sex that is pure so between a wife and husband. how can one gain the attention of a wise man who intends to marry and upholds The Way of Noble Ones.
With all due respect, many people overestimate their "achievements". Just because a once-returner has remainders of sensual pleasure &amp; anger, doesn't mean that he/she will act on those. It's of course all really speculation because none of this has been mentioned in the suttas, but I believe a sotapanna and even moreso a sakadagami has such profound level of anatta, that enables them to detach from sensual desire and anger quickly.

A Buddha would have no interest in being in a relationship.

Since you also mentioned that you are a misanthrop, I doubt that you achieved higher states because misanthropy is a generalized hatred towards human beings.

With regards to sex I guess no one can give you a definite answer because humans are way too complex, have different wants &amp; preferences in different life periods, and also their personal attitudes (and former experiences) can influence their relationship life &amp; sexual life. 

If you seek for a more loving relationship, make sure to look for a person who has somewhat same interests and goals as you do, and ideally both should practise Buddhism (or some other spiritual endeavor).