@Tooshay89 separated it into posts so it wouldn’t be even more insanely ridiculously long than it already was lol
So anyway....
Also, as for Cosmo, he will calm down eventually!! It helps to ignore them when you first come in. I’m sure you’re probably already doing that but ignore him for 5 or so minutes when you walk in or however long it takes for him to calm down and you can have guests do the same thing. Then that way he learns that A. It is not that exciting when people come in. It’s just normal. And B. No one pets him until he’s calm so it doesn’t do any good. He will, theoretically, calm down faster.
Or, if you’re not comfortable totally ignoring him for so long, just ignore him when he jumps or does naughty things and only pet him when he has all 4 paws on the floor. He can be as wiggly as he wants as long as he stays on the ground lol but totally ignoring him until he’s calm may be more helpful at first and then eventually you can go back to petting/greeting him right away because he will calm down a lot faster.
Sorry if you are already doing these things. Just figured I’d put it out there anyway just in case.
Oh and also exercise is huge!! I’m sure you’re already exercising him a lot but he could always use more! LOL exercise exercise exercise. A tired dog is a good dog

Although, actually, mental exercise/stimulation can be even more important than physical exercise! They can build up tolerance to exercise so that you just have a super fit dog that never tires out lol
Doing regular training, whether it’s obedience or tricks or whatever or both, can help keep him occupied. You can try teaching him new things as that uses a lot of mental power learning them.
Puzzle bowls or putting his food in wiggle toy can also help. Or training before meals. Anything that has him having to work/“hunt” for his food will wear him out. Having him wear a backpack outside may help too. Makes him think he is doing a “job” lol
And I am actually a huge fan of nose work for dogs. Especially neurotic/hyper ones or nervous ones and puppies LOL builds calm and focus because they have to focus on the scent and increases confidence because it’s fairly easy.
There’s all sorts of things you can do. Like hiding food around the house and telling him to “find it” or playing hide and seek with them, etc. can also hide toys and have them find them too. For find it, start with something easy like putting it right in front of him where he can see it and saying “find it” then build up to harder searches and blind searches and stuff cause otherwise he will have no idea what you are saying or asking LOL can also put food or a toy in one box out of many or under a cup or in one hand and have him figure out which one. With hide and seek, you can hide somewhere and call him or have somebody else tell him to “go find X.” He should have a lot of fun with these and they will be exhausting for him!
There is also an actual nose work sport you can take classes or compete in too where they use I think 3 or 4 different scents and there’s different levels. You start with one scent and easy locations and build up to harder searches but that can be a lot of fun. It’s based on narcotics detection training.
Agility may be something fun too even if it’s just setting up a couple obstacles in the yard rather than competing or classes. But it works the mind and the body at once which is nice.
Structured walks can help too. Asking him to do obedience or tricks on the walk or even just letting him sniff which I’m sure maybe you do being on the farm?
And I am sure he gets plenty of exercise running around the farm all day lol but I just thought I’d suggest some stuff in case you wanted to try it. Some of this stuff can be a lot of fun and I used to do it just because lol my dog was never hyper or whatever and actually kinda lazy but we loved training/doing this stuff lol well I did and he went along with it

but anyway, for a hyper dog it can be a godsend lol
But you are also right that a lot of it just comes down to age and maturity. Dogs in general take a long time to mature and they don’t really start calming down until 2 or 3 years old and until then they still need constant training and reminders. Goldens and Labs in particular are quite immature and can take even longer. Often they’re still goofy clowns until 5 or for life LOL but you should start getting some relief around 2-3
Anyway, sorry for the MASSIVE novel and the other. I know it’s probably super boring/annoying.
But hopefully at least
something in here was helpful haha