1) In last session 2 players killed a Daemon Prince and his bodyguards of 6 Iron Warriors without burning a fate point. I was thinking about giving them Crux Terminatus, but do you guys think that’s enough (they have done other thinks like infiltrating a Chaos Forge world at killing the head magos)
Why not? Sounds like you feel they've earned it, so go right ahead!
Personally, I prefer to delay such rewards a little if only because you want to create that build-up so when they finally get to requisition some Terminator armour, it really feels special, something they've been looking forward to for some time.
I like to think of it this way: yes, the PCs have done something incredible. However, the Crux Terminatus is an award granted by some pretty high ranking people. Given all of their responsibilities, it's likely that it will take some time before these people hear of the marine's exploits and then choose to act on them.
I don't agree with Herichimo that giving them the Honours early will ruin your game: you and your group get to decide what's fun for you. But, there is something to be said for withholding the Crux just a little bit longer, to see if not having it can encourage your players to do one or two more awesome things.