Maybe something about the front door spooked him once, or continues to spook him. Will he go out any other door without a problem while on leash? Is there or has there been anything flapping around the door? Weird noises or movements? Maybe a car backfired once while he was walking out the door. The floor could be too slippery there, or the doorway not bright enough and he doesn't like to not see where he's walking. If he only ever does it for the front door, then something might be going on with the door, or something happened with it in the past. When did this behavior start?
Also, I'm sorry to be blunt, here, but I have to ask. He goes for 3 1-hour walks a day--are these all on-leash? It's definitely a lot of time spent walking, but in my experience, walks on-leash rarely help burn off all the energy these dogs have. Off-leash in the yard helps, but only makes a pretty small dent, depending on the size of the yard. Vizslas I've known (to be fair, I've only personally known about 5 really well, and many others just a little bit) need to really get out, stretch their legs, and have enough space to really hit that turbo speed where they're practically flying. You know, the kind where their feet aren't even touching the ground. I certainly think Vs can adapt fairly well to certain levels of exercise (except for none at all), but it's possible he needs more time off-leash. Of course, I could be misinterpreting your original post and assuming all of these walks are on-leash all the time. If so, I apologize for the miscommunication! And if that's the case--wow! 3 1-hour off-leash walks a day would be very exhausting!
Anyway, I say that because more off-leash exercise might help curb some of the destruction of toys. Or it might not! Some dogs just really like ripping things up.
I will say that my dog became a little more gentle with his toys right around 18-20 months. He still likes to kill them, especially the squeaker, but they last a little longer. Sometimes he even treats them like his babies (it's adorable).
As for the constantly asking to play--yeah. Jasper does that too. I ignore it if I don't have time, and he eventually goes off and amuses himself. Sometimes that's bad, based on some chewed up books of mine! But the ability to go off and chew on a bone by himself came with age. Crating him for a few hours, even if you're home, is totally acceptable. It's good for dogs to learn that the crate is a safe space, a quiet space, and that it doesn't mean anything bad, just that it's quiet time.