Beginner - Need Help With Experimental Build

I'm on my first playthrough, and I could use some advice. I'm working toward an Intelligence-based character, the idea being that I'll have Pyromancy, Sorcery, and Miracles (via Velka's Talisman) with a magic or enchanted weapon. Please note this character is strictly PvE. So here are my questions.

1) What should I upgrade? Right now I'm using the Drake Sword for obvious reasons, but I'm as far as the Depths and have quite a few weapons (including the Astora's and Black Knight swords) to choose from and a fair amount of titanite sitting in my Bottomless Box. Should I upgrade and switch to another weapon? I also have the full Pyromancer, Chain, Elite Knight, Sorcerer, Thief, Hollow Soldier, Hollow Warrior, and Balder sets. Are any of them worth upgrading at this point?

2) What are my best endgame weapon options? Should I be aiming for Magic, Enchanted, or Lightning assuming Intelligence will be my highest stat?

3) How important is Poise for PvE? Does it reduce the amount of stamina drained by blocking attacks?

4) How much Humanity should I bother farming? I'm, in the Depths and need to do some soul farming, so I might as well farm Humanity, too.

1. Try out as many weapons as you can & pick what you like. i would upgrade 1 along the magic path and 1 normal path(to be buffed with magic spells) also take a look at MLGS.

2. End game weapons... See above.

3. Poise will help in pve by stopping you getting stunlock as much. Stability in your shield is what makes stamina drain less and makes it harder to break your guard when blocking.

4. If you only plan on pve 20-30 should be fine... U can always come back if you need more.

The MGS is a greatsword that scales with INT, but there are better alternatives, find a moveset you like and upgrade it to Enchanted.

Endgame is anything and everything aslong as its upgraded.

You could Phantom for hosts for consistent income and not very repetitive.