Advice / pointers on replacing valve seal

This weekend (hopefully) I'm going to attempt changing valve seals (cylinder 3 only, engine in car assembled) on my 440. I've never done anything & had a few questions I was hoping members with experience would be able to help out with:

How many psi should i set compressor at to fill cylinder?

Does the cylinder have to be TDC? If so can I just bar the motor over until I see the rocker raise and just start to come down?

What is the torque spec for the rocker assembly when I put them back on?

Can I just use a valve seal install tool to push the seal on the valve stem ? Will it damage the seal again or do I need like a straw / tube

Any additional advice / tips / tricks would greatly appreciated & sorry in advance for the academic questions. I would like to learn & tackle this myself rather than just paying to have it done
Why are you only replacing one seal (on #3)? Was it torn or broken? Normally it is best practice to replace all of them at the same time if they are cracking. Once they crack, they often are very brittle and start to fall apart.