Items Usage- Not "clothes" or weapons

[Fremen]

Hello everyone:

I'm new on this game (yesterday I bought the Apocalypse version under a friend's advice) and after spending this evening reading the forum I still have some issues.

1 - How many cards like "Police Dog" or "Face paint" can you actively wear/carry? (I mean by this the set of cards that have not any indications like footwear, armor, etc. but also are not described as one-use item or have a hand requirement)

2 - When the bonus of the card is applied?

3 - Do them have any kind of duration/uses?

4 - Are them considered combat bonus for the 7th seal opening? And could you give me some link to a detailed explanation about how is this bonus calculated?

Thank you very much and sorry for my english, it is not my native language