https://diablo2.diablowiki.net/Maces
Damage Bonus: This determines how you multiply the item damage by your stats to reach the actual damage. Each 100 points in that stat doubles your weapon’s total physical damage. All Maces are 110 Str, while most other melee weapons are 100 Str. This grants Maces 10% more damage bonus from stats.
TM being mace class (and hammer sub-class), the same benefit applies
From day 1 I’ve been a mace guy and I never knew about the strength modifier. I like that it implies that the bonus comes from stat points and not items. I also like the explanation as to how the 150% undead damage works. Thanks for the link.
It makes sense from an RPG perspective. Blunt weapons, more so than other types of melee weapons, benefit from physical strength, since the stronger you are, the harder you’ll hit with them. Whereas weapons like axes and swords take DEX points as requirements because they require more finesse, edge alignment and such for a clean cut. Not that mace martial arts don’t require finesse or anything, in real life it’s not like that. But it’s the standard RPG archetype.
That stuff is from a time where Diablo was still very strongly an RPG. Diablo 3 went away with all of that sadly.
Yeah, that may happen sometimes 
Only hammers (War Hammer, Maul, Great Maul and their Exceptional and Elite equivalents) have Strength bonus 110, all other maces have 100.
+% Damage = Strength * Bonus/100, so every 100 points of Strength grants +100% Damage to other maces (and most other melee weapons), and +110% Damage to hammers. So 300 Strength grants +300% Damage (* 4) to other maces and +330% Damage (* 4.3) to hammers.
Also from that page:
All blunt weapons in the game do 150% damage to the undead. This is like saying the item has a +50% damage modifier on it vs. the Undead. This adds 50% of the total non-elemental weapon damage on top.
+% Damage to Undead is added to off-weapon +% Damage when the target is undead, even when it’s on the weapon itself. So if you have +900% (* 10) Damage from Strength, Whirlwind, Mace Mastery and so on, then +50% Damage to Undead increases this to +950% (* 10.5) against undead.
Do you know off the top of your head if Act 1 merc can have up to slvl 27 to Inner Sight?
Not off the top of my head, but according to the 1.10 Mercenary Stats topic in the Amazon Basin’s D2 Technical forum, a Rogue can have level 27 Inner Sight at level 83 if hired in Normal, level 87 if hired in Nightmare and level 90 if hired in Hell.