You could try using his food as a training help. Put his jacket on him before putting down his food. Take the jacket off as soon as he eats or , at first when he will take a bite from your hand. After he is willing to eat then move his food so he will have to walk in the jacket to eat. My poodle would not wear a jacket and I did this to help his mind get out of that stuck mode. He still doesn't like it but he will wear the jacket now. My next thing is poodle shoes, fingers crossed.

We don't jacket up our dog for mid day pees even when it's -40. We just watch and even stand outside with him.

For his walk we put on his coat or sweater. He seems uncomfortable until we get started. The fact of the matter is that it's going to be winter every year. So whatever you do it's going to do you will have to do every year. I think either jacket for outside or not but he must go outside. Unless your willing to do something else every year from now on

You're going to have to leash poor Charlie and weather the cold yourself until he goes potty.

I've heard of people putting kiddy pools inside with sod during storms, if you have a garage or basement that will work for that.

That being said, after putting on and taking off his coat all yesterday when we went outside, my dog absolutely refuses to wear one this morning. I went out with him and stood on the porch while he did his business. I think going out with them helps them bear it a little more.

Note: my dog does have ~10lbs on yours though

For a little guy it might be an idea to get a cat box and litter box train him for the winter. It's not too hard to do and dogs are attracted to the litter box anyway (the joy of being able to dig indoors). It might be an easier alternative than trying to force him to wear things he simply refuses to.

Get a litterbox and bury some treats inside it for him to root around and get comfortable going inside. If he poops in the house stick the poop in the box. He should quickly get the idea that that's where his poops are supposed to go.

So, one thing that might help is leaving it around for him to see and get familiar with. then get him to come closer to it, maybe even interact with it/get his scent on it so its "his" and it smells like him.

another option is to harness train the dog (instead of a collar,) and then get a jacket thing that doubles as a harness. (this worked well for my parents and their nutter of a dachshund.) She learned quickly that the jacket meant she gets to stay out longer in the snow (hunting for rabbits and such like.)(She had no freaking clue what to do with them when she did manage to catch them, but, uh, we won't get into that.)

will he wear the rubber ballon type booties? I find the paws are a bigger deal than other stuff when its real cold and your just talking a few minutes of exposure.