That's your problem right there. If he isn't treating you well he can buy you all the physical gifts in the world and it won't matter, you still won't be treated well and deserve better

If he is treating you well the physical gifts really shouldn't matter and bringing up the lack of gift, aside from dinner and the flowers which are gifts, is exceptionally immature.

You need to take some time to reflect on why material things signal love to you. Trust me, I love giving presents and getting them, that's totally a huge part of how I show my love, but even I think being upset and hurt when he clearly made an effort through flowers and dinner is extremely spoiled and childish. It's the effort and consideration of you that matters, not the gift. He clearly made an effort. If you really were upset enough to make a big deal about your lack of gift given everything else you got that is a blatant sign that you are not mature enough to be capable of a healthy adult relationship. Does he do other stuff like the dinner and flowers to show he cares throughout the year? Is the answer is yes than you seriously need to reconsider your priorities. Because you are acting like a person no one who is healthy sane and mature and wants an equitable and loving relationship would want to date. You were wrong to be upset about the lack of gift. You are still wrong in that respect.

HOWEVER,

You also need to reflect on the fact that you have a way bigger problem here than the gift. Your boyfriend handles conflict very poorly and mistreats you when things aren't going well as a result. You're unhappy and don't feel loved, unless you're given materialistic things. That's really unhealthy (the part where you're unhappy and don't feel loved) and if that is a result of true neglect and inability to handle differences of opinion that is huge sign of his own immaturity. It's sounds like, based on what you are saying, he doesn't treat you well most of the time so you were expecting a gift on Valentine's day as evidence of his love in lieu of being treated well 365 days out of the year. That logic is really flawed. He should treat you well regardless of whether you get elaborate gifts or not. If he isn't treating you well that's the problem. If he routinely threatens to break-up with you as a form of emotional manipulation every time you fuck up, that's an issue. If the real problem is that he doesn't tell or show you in other ways that he cares than that is an issue too. That said, it sounds like he was hurt and acting defensive and I can't say I blame him. You definitely started this one. It also sounds like he did try to tell you and show you through the flowers and the dinner, so it might be less about him not telling you and more about your inability to listen. Your posts and comments are all about how you are feeling with no insight or care in regards to what he may be feeling when you completely ignore flowers and dinner and get upset about a lack of gift. That speaks more to how you care or don't care for him than the other way around.

In this case you're the one who has committed the bigger wrong by your reaction to JUST getting flowers and dinner for valentine's day. Stop and think about how ridiculous your anger and reproach was and apologize for that aspect. You also hurt him and made it clear that you don't appreciate his considerable efforts and only care about a gift. That may not be the case, but that is the message your inappropriate response conveys. Figure out what it is you need to feel love that isn't completely tied to the cheapness of a token gift you mistakenly feel he is obligated to give because it happens to be a holiday. If it feels safe to ask for that, be it more attention or a partner who works on his communication, then ask for that, not a silly gift.

His reaction, since you say it is a pattern, is also problematic. Let him know how much it bugs you when he threatens to leave every time he is angry. Admit to yourself and him that he was justified in being angry and upset with you as you truly acted inappropriately but that he is not handling his anger and hurt well and that that is causing bigger problems. His actions in response to his feelings are not okay. Create space for him to work on himself and change that aspect of his response. If he cannot do that and you cannot learn to appreciate non-material support more rethink the relationship and whether it is a healthy one.

But the first step is really going to need to be for you to admit that you seriously fucked up.