Weapon and Nonweapon Proficiencies (PHB, p.51-65): All in use.
Encumbrance (PHB, p.78-9): Basic and Mount encumbrances only.
Spell Components (PHB, p.85-6): For most spells, the character can be assumed to have the necessary components. Spells that have material components with a monetary cost will have to be accounted for, however.
Initiative (PHB, p.94): Group Initiative is being used. See the Combat Summary.
Weapon Speed and Initiative (PHB, p.96): Being used.
Parrying (PHB, p.100): Being used.
Exceeding Level Limits (DMG, p.24): While it's highly unlikely to come up, this rule IS being used.
Player Character Living Expenses (DMG, p.51): Given the events of the campaign, this rule will NOT be used for a significant period of the campaign. The players will be alerted when living expenses become an issue.
Horse Quality (DMG, p.54): Using this. Your DM enjoys the thought of inflicting nags, high-spirited pains, et cetera, upon his players, from time to time.
Weapon Quality (DMG, p.55): This will occur for weapons made by certain smiths. PCs proficient in those weapons will be advised when such are found.
Critical Hits and Critical Fumbles (DMG, p.86): In use. Critical hits will be double-damage on natural 20s, unless a natural 20 was the only possible roll that could hit it. DM will determine fumbles as they occur.
Hovering on Death's Door (DMG, p.104): In use.
Aerial Combat (DMG, p.106-108): In use, excepting the miniatures rules on p. 109.
Infravision (DMG, p. 160): Being used.
Other optional rules will be considered if proposed. The DM reserves the right to change the rules.
DMing done by Pip