Grabbing an opponent with wrestling only prevents them from dodging into another tile unless they can break the hold. How likely an attack made on a particular body-part is to connect and how solid a hit it would likely be
is random, though attacks overall become more likely to connect and hit directly depending on the abilities of you and your opponent.
Things that affect accuracy and damage can be split into four categories: attributes, skills, weapon, and armor.
Attributes: Which attributes are relevant depends on what attack you're using and whether your opponent counters by dodging, blocking, or parrying. Consult
this for more information (using a weapon to parry assumably uses the same attribute as attacking with it).
Skills:
Fighter makes melee attacks easier to land and all attacks easier to dodge, block, or parry (I'm not sure if it affects damage).
Skill with a melee weapon makes it easier to land an attack, parry an attack, and probably do more damage with that weapon.
Skill with a ranged weapon makes projectiles from that weapon more accurate, but I don't think it makes them do more damage and I'm sure it doesn't affect use of it to parry or bludgeon (that's decided by a skill for a different weapon).
Shield-user makes blocking with a shield more likely, but use of it as a melee weapon depends on the Misc. Object User skill.
Dodger makes you more likely to move into another tile to avoid an attack (which can sometimes leads to falling off a ledge).
Weapon: Weapon quality affects chances of an attack hitting
and damage. Not sure if it's carried over, but in 40d each quality level had a "roll" modification .2 higher than the last (so well-crafted is 20% more accurate and damaging than no quality, finely-crafted is 40% more, and so on until you have a masterful weapon twice as accurate and damaging as a regular one) and Toady has stated Masterful still has a 2 modified and artifacts have a 3 modifier.
The only effect weapon material has on accuracy is deciding the weight which can affect how easy a weapon is to use.
The effect of material on damage is
rather ridiculously complicated but can be simplified to "you wanted hard edged weapons and heavy blunt weapon".
For ranged weapons, weapon material is irrelevant to launching projectiles, only the weapon quality affects accuracy while ammo material and quality affects damage.
I know a shield's ability to block it not affected by material (except maybe a greater weight making it harder to use) but I don't know if shield quality is taken into account.
Armor: quality affects armor deflection chance the same way it modifies weapon accuracy and damage.
The effect of material on armor is also insanely complicated but can be simplified to "harder is better".
Armor has no effect on accuracy, just damage.