The shooting is a bit wierd currently. What was he shooting at you in close combat? Was he using pistols of any kind (includingc rossbow pistols)? If so, that's normally allowed, it's an extra attack unless they have 2 pistols and then it's all their attacks. Second, I've noticed that sometimes you think you are in combat with someone but you end up not being - usually it happens when you go to fight multiple people in close combat, you kill one and can't attack the other one in contact with you. These same warriors then seem to be able to fire missile weapons unhindered. The ignoring cover thing is a bit messed up, it's very hit and miss whether you get those weird shots that from some angles look like there is no gaps in the cover, or whether you are concealed, try and hide more at least until within charge range of everything.
To your second point on movement. the default human move/run is 4 spaces. Most people end up at 3 for a while because of the weight of armour. Whilst I've not added sprint to any of my human warriors yet, that does add one to the run characteristic so that gets extra movement. Were any of his warriors using crimson shade or magic for the flight of the zimmeranmovement spell? Those could be other explanations here.
To the 4th point, it could have been one of those games where your 99% chance toc ast spells fail a few times ina row, I've had it happen to me both pvp and in ai games, it's frustrating to say the least, but magic is very powerful so the failure here and there is a balancing thing. But yeah, could be an issue here or it could just be bad luck that game.