There were some clarifications about losing actions and that they would need to come from main actions first. But, I do believe that the topic I am looking for clarification on is slightly different. Or perhaps it is not and that is what I am trying to understand.

• Your investigator is Marie Lambeau
• There is only one card in front of you with doom on it.
• As your first action you play Moonlight Ritual to remove the doom.
• Do you still have 3 actions left? Technically you lost the ability to use a free action on a spell, but can't you say you used that to cast Moonlight Ritual?

Or does it have to be your last action of the turn to do that basically?

You still have 3 actions left. You HAVE to use the free ability action at the first opportunity to do so. You have no choice but to spend it on Moonlight ritual if you play it first.

Also, I don't think this really qualifies as losing an action. Its more in line with loosing an opportunity to trigger a free action.

As far as I remember, there is a rule (I don't have the rule book here right now) that goes along the lines of: "you first have to play the full cost of initiating the action (i.e. you already use that action), before the action is resolved and the effect triggered". So, by the time the doom is removed, you already used the free action that you get for having doom on a card.