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 Maltipoo, watch their mouth, their breathing and their body. A Maltipoo who goes off their food, chews on one side or paws at their face may have sore teeth. A honking cough when they are excited is their windpipe. From four years, trembling all over, when they are not cold or frightened, can be White Shaker Syndrome (a tremor condition seen in small white dogs). From seven years, a cough or tiring early can be their heart, and heart disease is on their record from that age. Bloat (GDV, a twisted stomach) can happen in any dog, though it is most common in large, deep-chested breeds. A swollen, tight belly, retching with nothing coming up, sudden restlessness or drooling is an emergency: contact your vet now.
Your lap is theirs. If they won't let you near their teeth there, tell your vet.