Deep Regrets

Yes — you reveal/select a Shoal and the top Fish is "on the hook" during the fishing action before rolling; Declaration (placing yourself at Sea or Port and equipping gear) is resolved in the Declaration phase before the Action phase. (p.5, p.6)

Yes — you may spend any number of Fresh dice (at least one) up to your Max Dice; Madness determines your Max Dice but you can always choose to spend fewer. (p.6, p.11)

Failing a catch does not force abandonment — if you can't or won't pay a Fish's Difficulty you must spend one die and draw a Dink, and that fishing action ends; Abandon Ship is a separate one-time action you may take if your lifeboat is face-up. (p.6)

For each Foul Fish you sell you must draw one Regret card, and the Fish sells for its current Madness-modified Value before you draw those Regrets. (p.9, p.10)

The number of Regret cards (public) determines your Madness level in real time, while Regret Value (the sum of face values, kept hidden) is used for end-of-game scoring; a flipped lifeboat adds +10 Regret Value but does not count as a Regret card. (p.10, p.11)

Spent player dice go to your Spent Pool, while spent tackle dice are returned to the dice bag; also, if a Fish's cost is 0 you don't need to spend dice to catch it. (p.6, p.9)