I realise that I live in a very different area but I would think those figures include totally feral cats and not just those who live both in and out
I'm fully inclined to agree with this. Total ferals, with no constant food source... three years, I see it. I always see that mentioned around here and I never see a study backing it up, if there is one I have to wonder how many factors are involved in that statistic. Indoor/outdoor, yes it is more risky, but not
that risky. I've known indoor/outdoor cats to die young from cars or wildlife, I've known others to live to a very old age. I think there's a learning curve and if they can survive that their odds of living to an old age just increased. Also I think some cats simply don't have the right mindset to be allowed outdoors, the overly friendly, overly carefree ones. And of course location is a huge factor as well, if you've got a lot of predators or a lot of cars... not a good idea to allow a cat outdoors unsupervised.
Blacky came to us from the street, she's been living indoor/outdoor 24/7 for 10 years now, in the summer she's outside 80% or more of the time. A lot of that spent in the sun room, technically still the house, but she can leave it any time she chooses. We live by a busy road but I'm not worried about her, she is terrified of cars and wants nothing to do with people, and hardly ever is more than 50 feet from the house. I know a lot of people that feed ferals (I volunteer at a cat sanctuary) and many of them are fed for years and years in colonies without premature death, a fair number of the volunteers feed stray cats (and have for years) or allow their cats outdoors as well. In fact we feed a feral as well, for a few years now one has come in to eat Blacky's food almost every night.
My cat Blaze was allowed on the balcony any time he wanted (except in winter when the door was often closed) but taking him outside into the big wide world was another story! He'd pee all over himself. We did eventually - when he was 15 years old - start taking him into the backyard regularly, at first he was absolutely terrified but he warmed up to the idea slowly and now he loves it out there... he wanders around spraying everything and eating grass, he has a great time.
Anyway, to the actual topic, I think your cat could just be meowing wanting the people to come inside, and that neutering may settle him down as well. Allowing him to get used to the outdoors is a personal choice, it may not be an instalove with them and the outdoors, and if you take the time to get them used to it you will definitely have to put up with a cat that wants outside a lot, and be commited to allowing them out often (on leash being the safest, of course).