Low isn’t too good. It seems that every rider that gets better and better a riding any style of urban unicycling (trials, street, flat) start from low but seem to get the seat higher when they get better. Now need to start low. That being said don’t ride as high as a freestyle* rider would. They ride with just like a road cyclist would, so pretty much the seat as high as possible while still being comfy. For trials you want to have a bit more leeway since you need to bend your knees for jumping and absorbing.
*Freestyle unicycling is not what freestyle is in the rest of the world, in fact it’s one of the least “free” styles there is. It’s done on a 20" (as opposed to 19" for trials) and done indoors, mostly. It’s awesome though: https://www.youtube.com/watch?v=LOEjDctiW8E
For now, as you are learning, you can definitely experience with moving the seat around a bit as you ride seat out/seat in font (or SIF). It’ll make you better at riding SIF. As for the pressure in the hand, if you’re in balance, a little bit of your weight in the seat, but you should focus on your legs more. You pull and push to help you correct your balance mainly, but the neutral will be without too much pulling. That being said you still have to keep your fingers and arm active.
Before we talk about where the seat needs to be, we have to talk about where you hand needs to be on the seat. You should be holding the seat behind the seat post. I know it may seem weird at first, but as The Mandalorian says this is the way.
If you are doing just little hops or standing still a little bit before an actual hop, you’ll want to rest your seat and/or hand/write on your inner thigh. Which side rests most mainly depends if you’re backfoot or frontfoot.
So either you will jump towards your back foot, or towards your front foot, but you will always jump away from your hand holding the seat. Since you are learning you can always change from right foot front to left foot front, or left foot front to right foot front, or even change the hand you hold the seat with.
Jumping towards backfoot: better for high jump, over bar and precision jumping and tucking in general
Jumping towards frontfoot: better for pedal grabs
I’m over simplifying here, but I definitely recommend jumping towards your back foot. Front foot isn’t bad per say, there has been many world champs that are front footed, but since you’re starting from scratch and have free choice, I’d say go back foot.
Look at this video of Mike Taylor and Aidan Teleki, the only two people ever to jump over 150cm. You’ll be able to see both rider hold the seat well behind the seat post and they rest their wrist on their inner thigh as lot, since both jump towards their back foot,
There is so much more to say, but I think that will suffice for now. I’ll leave this link to Márk Fábián’s Instagram account, current Trials World Champion. https://www.instagram.com/MarkPFabz/