Here's how to determine if most cards stay in front of you or not:
If the card is an Item (i.e., it has a value in Gold Pieces including 'No Value'):
- If the Item says "Usable once only" or tells you to discard it when using it, then it is used once and discarded
- Otherwise it stays in play
If the card is not an Item:
- If the card is a Race, Class, Hireling or any other special type of card discussed in the rules that says it stays in play, it stays in play
- If the card has a permanent bonus to your character (such as Really Impressive Title), it stays in play
- Otherwise, it is discarded after use
So yes, any Items or other cards that give you a permanent bonus listed at the top of the card stay in play.
When you are helping someone, you add your entire combat strength to theirs. You cannot give them partial support.