1 - Not much to add. I personally spend alot of time on the cloth map when macro-managing. Its laggy when zoomed in as you said, and I have Win7 64-bit, i7 965 exTreme, 12 gigs of RAM, and a Radeon HD 5870. I personally fixed the out-of-memory crashes that occurred every 2-3 turns late in the game with the large address aware patch https://forums.elementalgame.com/393090. The only crashes I get now are when messing with the various editors.
2-3 - Easy fix. This is a setting in the game options, Auto Turn. I turn most of these options off, but always leave Janusk ON. Always and forever...
4 - Not sure what you mean here.
5-6 - Some of the the tactical maps (viewable in the editor) have fewer than 12 possible attacker/defender start positions. This is bad because max army size is 12. Most notoriously the TacticalTestMap that is used as the default siege map on Kingdom towns with no walls. It has only 10 positions for attacker/defender, meaning some of your 12 guy army will be stacked up and/or stuck on the enemy's side of the board. Funny because if you're Empire, this one single map is often one of the most frequent you fight on when at war with Kingdoms.
Fun fact: The T_Desert_Grassland_Fortified is exactly the same as the regular T_Desert_Grassland (probably a mix-up).
7-10 - Tactical battles can be fiddly. I've had unexplained delays, irreversable loss of control (autocalc to get out). I've seen enemy units move and attack while their predecessors are still acting (this seems like it would actually be a nice feature, simultaneous unit moves by the AI to speed its turn up, plus it looks pretty cool).
Your units moving of their own accord is them carrying out any movement orders they were unable to perform from the previous turn. Sadly there's no indication of this queued movement until you see your 0 armor archers march inexplicably up to that Bone Ogre on the next turn.
About units not moving to the indicated tile. Its terrain elevation and big units that play havok™ on this. And some of those hills are really barely visible. A slight hill when viewed from any angle but top down will cause you to move to a different tile than you intended. This type of thing applies to units also. You have to rotate the camera over a large unit like a dragon to target a small spider or run the risk of targeting the dragon instead with no feedback until its already done. Also when units are engaged in melee, the lead guy inhabits the very edge of their square, which seems to make targeting the unit as a whole way more problematic than it should be. This last is probably the most annoying thing about tactical battles for me.
11 - Stacks are limited to 12 units. You can see if there are any ungrouped units when a new tab called Stacks appears next to Vitals/Actions. I wonder why the UI is only designed to display 11 portraits though, I always have to scroll over 1 to see the 12th unit...
12 - This seems to be a design decision. In CoreChampionsLevel.xml, it indicates that from level 6 each point invested in a stat gives a +2, and +3 from level 10. Of course this file also says there are SpecialAbilityChoices that are supposed to happen at 5, 11, 15.
13 - It doesn't cost any movement to exit a town, but it does to reenter.