He's lovely! A few words of advice, that I hope help.
First: Try not to worry or be anxious. At six months, he is very much still a baby - you have about another 6-8 months before he hits adolescence. Dogs pick up on human emotions.
Second: Do not be nervous. If you are worried about your dog showing affection to your child who is only a baby, then (gently) you are the problem. If you are that worried, then you need to keep them in separate rooms - although if his SA is really severe I am not sure how you should be able to.
Third: Unfortunately, you have a dog that is from two highly anxious, highly sensitive and very clinging breeds. Cockerpoos are very well known for extreme SA. At six months, he's really far too young to be left. You have to build it up super slowly over months, not weeks or days, or you will risk making it a lot worse. Most people I know with dogs prone to SA, including me, don't really leave their dog for more than 5-10 minutes for the first year or so - some people are lucky and manage to leave their dog for longer from day one, but that is 100% dependent on the dog and it sounds like your dog is not okay with that.
Fourth: When your child does start crawling or walking then, yes, you will need to keep them separate. Dogs are not playthings, they do not want to be touched all the time and they don't like children pulling at them/clambering over them/pestering them - and, unfortunately, that is exactly what young children do with dogs. They also do not like children rushing at them, jumping up at down or loud noises when they sleep - startled dogs can, and do, lash out if they are woken unexpectedly. You'll need to work on crate training.
Fifth: You need to give strong consideration now as to how you are going to manage the needs of the dog - not just sufficient exercise, but also mental stimulation - whilst you have a toddler at home who also requires 24/7 attention. In a year, your cockerpoo is likely going to need 2x 45 min walks a day (minimum), as well as stimulation throughout the day.
Sorry, OP, but I think whoever sold you the dog was incredibly incredibly irresponsible. It's lovely that you want to raise them together, but ultimately, you can't raise them together. Young children and dogs really do not mix - there is too much of a risk things will go wrong - and should be kept separate as much as possible until the child is old enough to know how to behave around the dog.
You clearly have the best intentions, but you're also clearly a novice owner, and you should never have been put in a situation where are you anxious and nervous about a dog licking your child - which is very normal behaviour and tbh you're lucky the puppy isn't biting, because puppies DO bite. The breeder was so irresponsible and I genuinely am quite horrified. I really hope the above advice helps, but you're in for a long, hard, road.