Some of this is not a training problem, and treating it like one wastes time your dog may not have. If they are distressed when you leave, if they growl or guard their food, their toys or you, if they are frightened on the lead, or if anything about them changes suddenly at any age, contact your vet the same day. A tip from a website, ours included, is not the answer. If it cannot wait, contact your nearest emergency vet now.
With a Vizsla, two things are not training problems. The first is panic when you leave: howling, scratching at the door, not eating until you are home. That is separation distress: contact your vet. The second is a moment that does not look like them, staring, snapping at the air or seeming lost, which can be a seizure. Film it if you can. A first seizure, one that lasts more than two minutes, or more than one in a day is an emergency: contact your vet now. So is bloat (GDV, a twisted stomach): a swollen, tight belly, retching with nothing coming up, sudden restlessness or drooling. It is most common in large, deep-chested dogs, so skip walks and hard play shortly before and after meals.
He'll keep leaning on you at the hob. If he can't cope when you close the front door, contact your vet.