As for your idea, I like it a lot. I'd quite enjoy seeing that system being improved upon, not just in the actual Harvest Moon but in a KS genre-bent game of sorts. It has potential, but nothing kills romance like doing nothing but waking up and giving an NPC grapes every day so that you can watch a cold, hard number go up until you win enough "marry me" points. That's like... the opposite of how actual dating is supposed to work. Absolutely no passion involved.
There was a dating sim that I tried out of curiosity (to date, the ONLY one I've tried) called Heartstring Bugs, and everything about that was either numbers or trial and error/luck. The numbers point you made is spot on, and the luck element was really overblown - say your wore the wrong colour dress, rather than for them to just go 'I think blue's your colour' or something, the person you're trying to date reacts REALLY negatively, which sucks. It's just a dress! Although I can't help feeling I picked a bad title, it does utterly kill any mood being set - but then, anything based as a 'sim' that works through numbers is always going to do that.
A lot of dating sims are like that. Just... bad. That's actually part of the reason I ended up breaking down and trying KS in the first place.
Oh, I'm sorry, did I get you the WRONG COLORED
EXPENSIVE-ASS JEWELRY?! Here, why don't you go to Hell, then come back when you're ready to stop being an insufferable bitch? Maybe next time I'll buy you the blue necklace, since I should have just freaking known
that's what you wanted despite never even having the option to talk about colors at any point.
And then it's weird because you'll go on the same date but with a different gift, and they act like the previous, near-identical date never happened. Kind of unsettling, actually.
Penile fracture. (Don't search for that if you know what's good for you.
I don't. I did. No regrets.