[Taqwus]

Welcome aboard. As a new player, you might want to check out Saber Cherry's 'stickied' thread titled "Newbies and Confused People - Look Here!" on this very forum.

As to your specific questions, hm.

- Scale effects:
*can't recall numbers at the moment but would not be surprised if they're in the Newbies and Confused People thread*

Order actually affects how much taxes you collect per capita at a given level of taxation. Unlike the original Dominions game, it does not directly affect unrest. e.g. Turmoil +3 no longer generates automatic unrest, but if you want to generate the same tax income as Order/Turmoil +0 with the same population, you'd need a higher tax rate, which WILL cause unrest + auto pop-reduction if memory serves; plus quelling the unrest will cause additional pop reduction.
Order also reduces the probability of random events.
Productivity affects resources, Cold/Heat affect taxation plus Cold+3 / Heat+3 exhaust troops more readily, and certain unit properties and equipment may be affected (heat auras stronger in heat dominion, ice armors stronger in cold, cold-blooded units tire easily in cold provinces, etc), and certain spells are also affected (Heat from Hell stronger in hot provinces, say), Magic affects research speed (1:1), magic resistance (-0.5, round down IIRC), casting fatigue (something like 10% less base spell fatigue), Luck affects probability of events being good/bad and of frequency IIRC. Growth affects supplies, and positive growth is the one way to have population growth; death scale slowly kills. Growth/death is something like 0.3% pop/turn.

- Communion items... certain items automatically cast spells either at beginning of battle or every turn. Communion slave/master matrices auto-cast at beginning of battle.
A communion master, for that battle, gains +1 in each path he already has if he has 2 communion slaves, +2 if four slaves, +3 if eight slaves and so forth if memory serves. In addition spell fatigue is split among the communion slaves. Hence, this is one of the more practical ways of casting the REALLY powerful, fatiguing high-end battle magic that take 700+ fatigue and very magic level. Also, spells that would otherwise affect only the master (Body Ethereal, Invulnerability, et al) also affect the communion slaves. Masters can share slaves.

Die rolls are frequently open-ended 1d6; IIRC, the first roll is 1-6, and if it's a 6, add another 1d6-1. If the 'die' came up 6 again, keep adding and rolling until it stops doing so. Potentially a blowgun dart could kill a perfectly healthy Wyrm in its own max dominion; it's just not very likely. In the case of attack and defense, two of these open-ended dice are rolled for both attack and defense.
unit attack + weapon attack + any other modifiers (e.g. bonuses from magic, whatever) + 2 open-ended d6 vs. unit defense + armor defense + whatever other defense modifiers + 2 oe d6, if attack total exceeds defense total it's a hit. Same thing goes for damage vs. protection.

Mages; friendly fire is definitely an issue. You can help somewhat by choosing their first five orders (suggestions, really; they may be disobeyed) on the same screen that lets you assign formations. You can boost their precision with certain spells (Aim, say) and items (Eye of Aiming; only give one!). Mages may not be given specific targets as that would be a bit unbalancing (Soul Slay versus enemy commanders, say) and perhaps unrealistic (you have an omniscient view of battle, but they don't!). Some spells such as Curse seem to target 'big first' almost always, others seem to be hit or miss.

Bow of Accuracy AFAICT is nothing special other than the unusually high prec rating. If you /always/ want to hit, you probably need a prec-100 spell like Incinerate, Soul Slay, Paralyze, Disintegrate (IIRC, not sure about this Last one).

Re: afflictions, there's also the Faerie Queen (requires high Conjuration, and Nature 5 or so) who can heal like a Priestess (may not be as effective, it's not specified), and one of the T'ien Chi national heroes does this too. Immortals automatically heal afflictions with time, as do units with the 'recuperation' flag (quite a few Pangaea units, the unicorn-riding national heroes, a few pretender chassises, others perhaps). Gift of Health is a very valuable global enchantment for those with robust troops likely to suffer afflictions rather than dying outright.

Weapon length: forces morale check.

Survival skills apparently reduce chance of suffering from starvation. I'm not sure how it works, but they still do nominally require full supply.