My current choice for Torreador and path on the main problem:
The Warrior on the easy path, with the shield and all the campfires:
Enchanted Shield, Campfire, Jaw Worm, Campfire, Campfire, Campfire, Campfire, The Collector
Reasoning
I tried to find scenarios where a Hero had a 100% win rate against The Collector (given that they made it to the boss battle) and found one: when the Warrior had at least one of the two Warrior-specific treasures (Shield, Armor) and only faced 1 enemy along the way he had 228⁄228 wins. That included 31⁄31 wins when it was his only useful treasure (out of the 6: Shield, Armor, Boots, Cloak, Potion, Ring).
And would he survive that path to The Collector? The Warrior never lost to the Jaw Worm, and never lost to the first Enemy he faced. And only lost on floors with a Boss or Enemy. So making it to The Collector seems safe.
Looking at the bonus objective, the Hero and path that looks most promising is
Warrior: Gremlin, Jaw Worm, Adamant Armor, Enchanted Shield, Sentries, Campfire, Vanishing Powder, The Champion
Reasoning
This run looks promising at first glance because it gets the two Warrior-specific treasures, and faces as few enemies as possible subject to that constraint (as the Warrior seems to fare better against bosses when he has faced fewer enemies).
The big concern with it is the boss battle. The Warrior did ever lose to the Sentries, but only about 2% of the time, and never when he had both Warrior treasures. And he never lost to Gremlin or Jaw Worm.
The Warrior had only an 87% win rate against The Champion when he had both Warrior treasures, including an 86% win rate when his other floors involved 3 enemies, 1 campfire, and 1 other-hero treasure (as this plan does—Vanishing Powder is a Rogue treasure). And one of the failed runs (23970) looks very similar to this plan: Staff of the Magi, Enchanted Shield, Slaver, Jaw Worm, Adamant Armor, Sentries, Campfire, The Champion. So this doesn’t seem like a guaranteed win.
But I don’t see anything better at this point. A Rogue run which gets the Cloak of Protection and the Vanishing Powder looks like an obvious alternative, but looking at similar runs that seems worse.
And when I look at win rate against The Champion in runs that made it to the final floor, by Hero & pairs of floors previously encountered, the top 3 highest win rates all involve the Warrior with Adamant Armor and another useful treasure (Boots of Swiftness, Enchanted Shield, or Cloak of Protection), each with a win rate of ~87%. So that includes my planned run (Hero with Armor & Shield) basically tied for first. None of the other floor pairs with a win rate over 65% look possible in this tower; Rogue with Cloak of Protection and Vanishing Powder is down at 55%.