We had more luck with toilet training (at around the same age) when I started taking mine out for a walk on a lead along our road every hour, rather than standing outside in the garden waiting for her to go while she got stressed. She was happier to go outside this way as it was more interesting and the whole process often took less than a minute as she would wee when distracted and wee within a few metres and we would then go straight back inside. Going every hour (unless asleep) gave her fewer opportunities to go inside and over time going inside felt alien, so she started asking to go out into he garden. As she got older I increased it to every 1.5 hours, 2, 3 etc and at around 9 months (when she was reliably not weeing inside and asking to go out) I noticed she was able to hold it for 10 or so hours.
Mine also pulls when she doesn't want to go a certain way on a walk and I just stand there and face the way we are going until she decides to comply.
Mine doesn't like getting cleaned either, so we chose to pick our battles (and that wasn't one of them, whereas rolling in animal poo would be). We have a hard floor downstairs, so when we come in from a wet walk she is not allowed in the lounge that has a sofa or upstairs until she has cleaned and dried herself. She stays in the kitchen where there is only the crate to sit in. Could you do something like this and maybe put an old towel down at the entrance to the house that he would naturally walk on to absorb any excess mud?
Personally we chose not to impose physical procedures like putting on a harness, cleaning etc as she was becoming increasingly unhappy about it and we have children so didn't want to take the risk. She is not in charge in the house and we have developed verbal ways of getting her to do what is needed, such as jumping into the crate in the car rather than being lifted and on the occasions where there is no choice (like being lifted onto the vet table and restrained for examination) it has actually been ok, I think because she now trusts us.
At the weekend mine started having a reaction to something from running through a bush and I knew she wouldn't be happy to be wiped down, so we took her into the garden and turned the hosepipe on. She wasn't very happy about that either but it did the trick and there was no aggression. Another time one of the children spilt honey on her head so I tied a wet cloth to the end of a stick and wiped her with it from a distance - she ended up enjoying it!
She will be 2 years old at the end of May and we have noticed she is a lot easier to manage generally in the past couple of months, so it does get easier eventually! As others have said, he is very young and it does take time for things to start working. I spent ages asking mine to leave a room by saying "out" and either throwing a piece of food or using my body (not hands) or a piece of furniture to shepherd her out by walking towards her and all of a sudden with maturity that isn't needed and she responds to "out" on it's own.
One option could be to try a more hands off approach for a week or so and develop some other strategies and then review what you are doing and see if it helps.
There is a chance that your pup isn't used to the collar, or possibly the weight of the leash. See what he does if you clip the leash to the collar and let him drag it around the house. It will allow him to get comfortable with the weight of it and maybe help him fell less "trapped" by it. A lighter leash might be beneficial, or a smaller leash clip.
