Wanting to getting into tabletop, have some questions

Hi! So I am a big fan of warhammer lore and have been thinking into making an army of my own to learn the game with, but I am in an awkward spot because my favorite legion is definitely the pre heresey emperors children so that leads me to a bunch of questions!

1. I already have an idea for a successor chapter I'm playing around with, but what codex would make a good base to use for it that could focus on close rand swordsmen with bolt pistols or something similar!

2. Could the palatine blades squad minis be used in 40k? I think they're absolutely beautiful and fit my vision for the legion.

3. Is it possible for A space marine to use xeno weapons on the tabletop? I am fascinated by the lore of them taking blades as trophies and training with them until theybare better than their original owners.

4. If I have a (shameless OC) named character I want to make special, are there unit types that would distinguish him from the rank and file like a chapter master?

5. Would it be possible to somehow use the loyalist Fulgrim clone on the tabletop?