He’s saying all the good men died in the war and the rest are all 45 now and married up.

Ah, OK. Thank you. I assumed she was in the novel. My mistake. One more thought: if this is set in 1975, which I think is when the film was first released, then 35 years earlier was roughly when the USA joined the war, after Pearl Harbour - and I imagine a lot of fit young men left lots of small towns to join the military forces ...

Thank you very much, Michael! Your explanation is really good. I would've never been able to infer all you said on my own. Just a bit of clarification: the daughter was put there by a fan; so she wasn't actually in the movie. I just thought that her narrative might shed much more light on the scene than my fumbled account of it. I agree with everything you said but one thing: I don't think Quint saw Brody's attempt to get rid of the drink - he simply didn't need to, as Brody not drinking it in one gulp was enough for Quint to understand that his visitors were nothing like good old men this town was full of some time ago. Brody sipping at the drink: https://ibb.co/nPcmp7w And Michael, do you mind putting your explanation in the answer section? That way we'll be able to close the question. I'm pretty much sure that your explanation addresses almost everything one could possibly want to know about the two lines.

In some societies, the ability to handle hard liquor - to drink shots of very strong alcohol without flinching and without appearing affected - is taken as a marker of masculinity, of being a man. In this scene, Quint supplies his own home brew- - by the accounts in the scene, fiercely strong and almost undrinkable - to, first, his estranged daughter, who narrates the scene, and then to his other guests. His daughter of course downs the drink and doesn't flinch: she grew up with it, probably. But the men don't ; they sip at the drink rather than down it in a gulp, and try to hide their attempts to get rid of their shots while Quint isn't looking. Of course Quint sees: he is using the alcohol to get a measure of, to inform an opinion about the qualities of the people who have come to see him. He is not impressed. "Can't get a good man under 60" -- in this town, you can't find a good man who is younger than 60 years old (that will include his visitors, but not him.) "All gone at least 35 years." I read this as US, informal for "they have all been gone since at least 35 years ago." I suspect the back story in the novel, and probably the film - I think the implication is that this small (fictional) seaside town, a failing resort town dependent on summer tourism from New York (and not yet home to a mega-casino, organised crime and the visitors that those might bring), has been losing its best men to the city or to other migration for years. There's nothing in this small, failing resort to keep a good man - a tough, ambitious, enterprising, reliable guy, the kind of guy who could down a shot of firewater in one and not blink, who could stand beside you in a firefight or a battle with a giant killer shark and who you could trust with your life - those kinds of guys have all been gone for years. No wonder his daughter left town ... https://taskandpurpose.com/entertainment/the-darkest-moment-in-jaws-had-nothing-to-do-with-that-shark

That's not from the movie, and to me it makes no sense.