Having to go back & replay previous chapters if you didn't score enough points in flashbacks: Ridiculous & bad game design.
TIP FOR OTHER PLAYERS FACING THIS: Download Unren, run it in the same folder as the exe & press 9 on the menu to unpack the whole game. Open Game folder, then open sc_5_6_fb in notepad. Search for Angel_Coins and adjust the amount you're rewarded and/or the amount of angel coins each expense costs (restaurant, ring, bouquet) so you can get the most expensive of each.
While I don't think "failing" the flashbacks are a good design idea in general, I can live with them when you don't have to literally reload previous chapters - unsure which even - just to play back up to the current to only possibly have made the right arbitrary choices to continue playing.
Also, seeing as this is a choose-your-own sex adventure type game, players often (as in my case) don't make the arbitrary "best" choice on purpose. In mine, I wanted him to be a good guy, with the fiance as sweet, but just a little out of his league.