Is Ethan gay?
Sexuality is also a tricky subject, in literature as well as in life, and it's not always possible -- try as people might -- to put someone else in a neat little box. Your question is good, of course, and if you want to continue to explore the subject, I would recommend that you do a literature search, using a good database (such as MLA) and key words such as "ethan frome" and "sexuality." You'll need to find an institution (such as your school) that subscribes to that database.
Two articles that are likely to show up in your search are: "Cold Ethan and 'Hot Ethan'" (1987) and "Ethan Frome and the 'Springs' of Masculinity" (1996). These articles aren't all that easy to read, but I bet that you'll get something from them and will be encouraged to explore the topic further.
In any case, I hope that you will move past stereotypes such as whether or not a male character being "sensitive" or "indecisive" is a sign that he is gay.
Ethan Frome certainly is a very disillusioned man with a frustrating set of circumstances that have prevented him to live his life to the fullest, but I do not see any correlation between his depression and any possible homosexual tendencies.
However, I do want to say that under the conditions that he was, confusion of self and life is imminent, and if he had found himself questioning his own sexuality it would not have been any differently than when he question his own relationship and fell for Mattie. In fact, the conundrum that he felt was open to many questions about himself he could have asked and he was indeed quite sensitive, but I do not believe that he was gay.