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 Labrador, watch their appetite and the way they move. A Labrador that leaves food in the bowl is telling you something. So is one that licks their paws for hours, shakes their head after every walk, takes longer to get up, or stops wanting to jump into the car. In an older Labrador, pacing or staring at night can be the start of cognitive decline. Bloat (GDV, a twisted stomach) is most common in large, deep-chested dogs, so skip walks and hard play shortly before and after meals. A swollen, tight belly, retching with nothing coming up, sudden restlessness or drooling is an emergency: contact your vet now. Put the rest down to habit or age and you can lose months.
They'll keep bringing you shoes. If they stop meeting you at the door, tell your vet.