Its actually not unusual for a vet to say that, we was told the same but in reverse, we had our first springer done and it did make him a little nervous tbh so when we got harvey i qestioned whether he should be done or not as his temprement was spot on and dint want to change him and the vet said as he was about 4yrs by this time it wouldnt change him as his character was already formed at this time, So no it isnt wrong advice just the vets views maybe.
Ignoring bad behaviour is what a lot of people struggle to understand and i can see where you are coming from. First make sure there are no temptations on the counter if he does jump up, command him with "down" firmly but not harshly them immediately treat him you are going to have to have high value treats available because this had to be done within 3 to 5 seconds for it to be effective, if he lunges for anyone (think you mentioned he does that) bring him right to your side with a "no" (not punished) wether he has come to your side voluntarily or you have brought him there by leash doesnt matter it had to be a "good boy" and an immediate treat. This is ignoring bad behaviour and rewarding the good. Nothing will change overnight and there will be times when you want to give up as its having no effect but believe me he will be learning all the time before any signs are shown so please dont give up. Nothing you do should be negative everything needs to stay positive.

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