Medium armor isn't quite as good as the absolute best Light or Heavy armors, but that's a minor detail. I had no problem completing the MQ with a character using seriously underwhelming equipment (a mix of mostly Imperial Dragonscale and Imperial Steel, with a couple of miscellaneous pieces thrown in; Orc armor is better than any of those). Morrowind is fairly forgiving, and at worst it might take you a couple of extra levels before you can do the same thing with lesser stuff.
The best Light Armor can actually exceed the protectiveness of Medium, BUT.....and it's a major issue.....Light Armor will NOT count toward building Endurance, so your hitpoints will suffer in the long run. Either Medium or Heavy will count toward increasing that Attribute.
Orc armor is one of the best Medium armors in the game (unless you count the expansions), and more than sufficient, if your character develops sufficient skill in it. My advice is to just play the game and do what the character would do.
Marksman can be tough to learn, because you can't hit the broad side of a Netch to gain experience in it. Once you do become proficient, it's overwhelmingly powerful in many situations.
Mysticism can be a powerful school, although Enchanting or Alchemy are potentially more versatile (enchanting being difficult to start with, but overwhelmingly effective in the long run). Alchemy is so easy to abuse and to such extremes that it's funny, until your insanely "uber" potion won't wear off for another 17,283 seconds; then it's annoying. I also like Alteration, which is good for getting into awkward places like Telvanni wizards' towers, mountain tops, or high ledges, etc., but an Orc makes a poor "direct" spellcaster, so I prefer potions and enchanted trinkets for an Orc character.
I think you have almost all the bases covered, except one. Long Blade and Armorer will boost Strength, Medium Armor and Spear will increase Endurance, Marksman will increase Agility, Speechcraft will boost Personality, Athletics benefits Speed, and Restoration will raise Willpower. You're short one skill for Intelligence, unless you're intending to play a stereotypical "dumb Orc", which doesn't seem to fit the rest of the description. That could be handled with Alchemy, Enchanting, or Lockpicking, although the last doesn't seem to fit the character.
Otherwise, a very decent build, and quite playable as is.