(1) Well, in theory you could rename files, not recommended though, since files transport a bit of information. In game no.
(2)
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Most of the info you are looking for is in this part of the character window. "Fit" is a value 0-100, the higher the more fit you are. "Big ass" is decided by the "Hips" value.
You are "younger" or "older" based on your age in respect to the character, so if you are 27, you want the 31 yo to like younger people and the 18 yo to like older people.
Hair and eye color are spelled out on the right directly. "Med" means medium, so not affected by either the dark nor the light bonuses. Otherwise it would spell out "dark" etc. "Short" after hair should be self explanatory.
Height: 6-1 is average, anything above that is tall, anything below is short. However, when you create a character and compare the values, you will see that there are only three (I think 5-10, 6-1, 6-4), the highest being "tall" and the smallest being "short".
So with this character I want girls to like fit guys with a big ass and short hair. I don't care about their eye color, hair color or height preferences.
(3) There isn't, however you can save scum. Save the game, go to the park. She's not there? Reload, go to university (entering and leaving library are not an action). And if necessary reload again. Or you could text her and know where she is from the start.
Also, four "non actions" (like sending texts to girls, walking through your club, etc.) will move time forward, however this will not be saved, so if you save after three walks, then go somewhere else and time moves forward, then reload the save you can start the counter anew.