Alright just confirming I have this all squared away:

1. Saruman readies himself anytime you play a card with doomed, including Grima adding doomed to a card and an ally gaining doomed to trigger an effect such as greyflood wanderer. Also still works if Grima reduces the cost on a 0 cost card and adds doomed to it right?

2. If Saruman has Fall of Gil-Galad attached and is defeated, you can drop your Threat by 13?

3. Similar to the above if you lend out Saruman with Desperate Alliance you can then drop your Threat at will with any cards?

4. If Saruman has his text box counting as blank you can Threat down at will?

Thanks for the help in advance!

I think you're good on all of the above.

Explanatory note on #1: Gríma actually does two separate things to a card—one does not depend on the other happening. So you do not have to "actually" lower the card cost to gain the Doomed.

Quote

Action : Lower the cost of the next card you play from your hand this round by 1. That card gains Doomed 1. (Limit once per round.)

Thank you!