The nut slot height is all relative to the top of the first fret, so you really need to look at the string clearance over that to decide whether the nut needs a bit more filing. You could just have a go at the slots with a round needle file and some P400 sandpaper to lower them whilst it's fitted to the neck. That's how I do my bass nuts.

In theory, truss rod should really just be used to set the neck curvature with a small amount of neck relief, and action then adjusted with the saddle heights. But I must admit I then almost always tweak the neck a bit flatter to get the action down a bit more.

I'd really recommend giving the headstock a bit of a shape. You'll make the bass look so much better.

In the past, for the 4-string MM-style kit, the pickup has come configured for parallel operation, with a volume pot for each coil and a common tone. https://www.pitbullguitars.com/wp-co...MMB-4_2014.pdf some of the wiring is done at the factory and isn't shown. So if that's a kit pickup, it may be worth double-checking the wiring arrangement on it. But the factories do chance things from time to time without notice, and the 5-string version may also be different to the 4-string.