I dislike the things you mention. I mostly hate toxic couples, non-concent/rape and sad endings. I usually don't like stories that take place in school, I guess because they act immature. I'm gonna share some of my favourite romance series and I will mention if any of them have one of the things you hate.
I feel you linger in the air. I doesn't perfectly fit but I think you would enjoy it. It's a historical thai romance. The couple do break up but it's just for a short bit and it's a mutual decision. They are gay and he is supposed to marry a girl for his futures sake (I would not call it a love triangle, they never get together or like each other). It's a really good series, good writing and story, very romantic and it has a healthy relationship. They communicate and care about each other.
I told sunset about you is basically a must watch, it's a great series and just 5 episodes (it has a second season but it's not as magical). It has "love rivals" but only because they don't realice their love and one of them struggles with his sexuality.
The eighth sense. They do break up for a bit but it's because he is traumatised.
For a "lighter" watch try Old fashion cupcake. It's just 5 episodes + an epilogue, so they get together in the last episode but they act like they are dating and it's really wholesome. If you like Cherry Magic then you should like this one.
About youth is also good, they may get together later in the series, but it's just 8 episodes and it's wholesome.
Bokura no Shokutaku/Our dining table is wholesome and just ten episodes but they get together late in the series I think.
Our dating sim is wholesome fluff and just 8 episodes.
You may also like (for these I also think that they get together later in the series but they are quite short): Seven days: monday-thursday, Seven days: friday-sunday (two movies). His (this is a movie and it's more serious/dark). You are mine (this one is a bit toxic). The eclipse. Love tractor. The new employee. Like in the movies (they break up for a bit). My ride...........