well its kind of difficult to guess without seeing pics but it seems like you have 2 problems so I’ll take a shot at them individually.
first for your texture problems:
have you unwrapped and checked your UV’s in blender?
have you assigned the material slots in blender?
for the disappearing faces:
have you tried recalculating the normals before exporting?
those are just guesses at possible causes but I hope it helps:)