First build DJT-1 bk

[McCreed]

Hi Christian, and welcome!

For the finish, im thinking a seafoam green stain with tru-oil on top, hopefully extra glossy.

Just be aware that Tru Oil has a slight amber tint to it so can alter the base colour slightly. There have been numerous accounts of blue guitars turning green over time. I don't know how sea foam would react with the amber, but I thought it worth mentioning.

...im a bit concerned about 6th and 7th frets beeing a bit short but maybe not critical..

I can't see the fret ends clear enough in that photo to determine if there will be a problem. If they're too short, send a close-up photo to PBG and I'm sure they can help you.

The nut is taller on the bass side but the grooves seems to be deeper and kind of even with the treble side, guess I have to sand the top to make it look good with the neck radius? Ordered the bone nut upgrade and it looks the same, is this normal?

With regard to the nut, that's not uncommon. Different manufacturers cut/shape their nuts differently.
Looking at your photo, I would bet that if you measured from the bottom of the two E string nut slots to the bottom of the nut, the distance would very close if not equal.

Also, pre-cut nut slots are mostly a guide for string-to-string spacing and 99% of the time require adjustment to the individual string slots to achieve correct nut action.

Edit to add:
Profiling or finishing the top of nuts is whole other conversation. Like most things there are varied opinions and approaches on what is "correct".