My SO and I started doing "family dinners" with friends rather than going out most of the time. We go over to one of our houses and cook/hang out. Sometimes I'll make homemade pizza, or we'll roll sushi. Last time one of the guys smoked pork shoulder and made some bread (before the get together). The cost of making pizza for 6-8 people is around $20-30, same as a restaurant meal for 2 people. We don't drink all that often anymore, but occasionally if someone asks what to bring I'll tell them a 6 pack.
27-29 year age range in the group. My buddy and his girlfriend go out and do things a lot and spend a good bit on it, but we don't feel guilty not joining. We meet up for dim sum or something like that every month or two, the rest of the time is at one of our homes.
Valentine's day out is always going to be expensive, because restaurants often change up their menu for that day. Why not make something at home and go out the next weekend?
As for the birthday, you paid other people to cook/serve/clean up after you all day, along with serving you drinks, and weirdly expensive bowling. I'd say you got a pretty good bargain to live what in most times would be the life of royalty. Brunch, then bowling, then cocktails/appetizers, then dinner is a pretty full day of eating out. The brunch seemed a bit pricey, and the bowling is ridiculous. If you want to cut costs without cutting experience, it's just a matter of not doing the little convenient things every time. Don't get nachos with happy hour, get something smaller for brunch, etc etc.
It's like going to Top Golf, you can spend $10/person for 2 hours of golfing, $15 with a beer. If you want multiple beers and nachos and a few shots it can quickly shoot up to $50-100/person. Does having 3 beers, some shitty nachos, and a round of tequila shots make the event 5-10x more fun than 1 beer? Probably not, so don't do it. Be efficient about what return you're getting from your money.
Occasionally it's worth just not worrying about it and spending more than you should. Key word here: OCCASIONALLY. SO's birthday should almost if not always be one of these times.
There will always be a special event, or a friend who says "come on do it just this one time, we never see you!" If you have 10 friends you see once a month each, you'll have a "once a month" spending experience every 3 days. On average one of those friends will have a birthday every month, combined with yours. If they're doing something spendy just pretend you're on a diet or a "cook at home challenge" where you can't eat out for X amount of time (better yet, DO the challenge). Offer to cook them food at your house instead. Eventually they'll probably reciprocate. The first few months you probably won't save much money because it will often be at your house, then once they're into it you can suggest doing it at their place or ask them to bring sides/ingredients. Even offer to cook/help cook at their place if they get the supplies.