Can you put the "A Score to Settle" elite upgrade card on a rebel or imperial pilot upgrade slot?

This card requires the use of a debt to pay condition card

Yes, unless a card lists a restriction such a 'scum only' it can be used in any faction.

Silly question. Does it apply for all my ships? Or only the one that has the upgrade card?

'You' and 'your' always apply only to the ship, not the player.

21 minutes ago, thespaceinvader said:

'You' and 'your' always apply only to the ship, not the player.

Thanx. I tried to convince a player it didn't work, but I didn't have any argument.

That's in the core rules. Can;t remember the page ref, but I'm sure someone will provide the citation shortly.

3 hours ago, thespaceinvader said:

That's in the core rules. Can;t remember the page ref, but I'm sure someone will provide the citation shortly.

It's on page two if the RRG.

CARD INTERPRETATIONS
Many Ship card abilities use the word “you” to refer
to the corresponding ship. Upgrade and Damage
cards that use the word “you” refer to the ship to
which the card is assigned.

Also card abilities in the Rules Reference Guide

• The word "you" on a Ship card refers to the corresponding ship. Abilities on Ship cards cannot affect other ships unless the ability specifies otherwise.