There's pages and pages of story and gameplay concepts in the Ideas Dump thread. Use them as you wish, and change details if you want.
But regarding a stat-driven game in which the main character has a small amount of time in order to be paired with a romance option... the first thing I'd recommend is looking at the dating simulations which people have already created
. Please keep in mind that about 1/4 of the games listed have adult content.
Other things I would recommend:
* If you understand Flash, go ahead and use it. But you don't have to. Some of the games in the VNDB list were created with Ren'py, and one was made with RPG Maker XP. Use any program which fits your purposes.
* How much do you want to emphasize gameplay, and how much do you want to emphasize story? The freeware version of "Hatoful Boyfriend" has a small amount of gameplay, and is mostly text (and comedy). "Heartache 101" has a completely skippable opening sequence with about ten minutes of story. The main game has some dialogue, but it's mostly about statistics, dice-rolling, and the main character's actions.