Interesting list of ideas. Couple of thoughts:
Suggestion 1
As someone who loves to be the Howler because I like playing a support-class for the zombie team, I like this idea. By allowing the Howler to gain an income through buffing zombies, that will give more players an incentive to play the Howler and prevent it from becoming an obsolete zombie boss.
Giving players a reward for playing as a support-class is something that needs to be reinforced for Zombie Survival, and starting it off with the Howler is a great way to go.
Based on the values you provided for how many points it would receive per certain number of zombies buffed, I would keep it in multiples. For instance, for every 5 zombies buffed, the Howler gets 1 point, for every 10, 2 points, etc. Keeping it where the additive points is set to 5 buffed zombies = 1 point rewarded would be small compared to how many points zombies could make by just slashing at a barricade, but it's better than nothing.
The reason why the value is small is to ensure the Howler doesn't become an easy point-farming boss; playing as a normal zombie that slashes at barricades and humans will still be more profitable than what the Howler could make, but at least the Howler is making something.
Suggestion 2
I like this idea. Giving players the opportunity to decrease one of their card's levels to earn back the points initially required to level it in the first place is a flexible suggestion. Something like this would mimic a common game mechanic of re-spec in videogames with skill trees involved, and something like this is not too different.
If there's one thing I'm worried about is that there's no mention of whether you earn your cards back or not.
If it was up to me, I would make it where should the player choose to downgrade one of their weapon cards, they would earn back all the points initially required to level-up, but they wouldn't earn back the cards. Basically, the cards on-hand would neither increase nor decrease; that would remain constant, but by downgrading a card by one level, the player would essentially "lose" cards that they used up to raise it by a level.
Ex.:
I have 784 "Crossfire" Glock cards on-hand, and my current "Crossfire" Glock card level is 7. It costed 1000 points and 400 "Crossfire" Glock cards to level this card up to level 7, and if I choose to downgrade this card back to level 6, I would receive the full points refund, but not the full "Crossfire" Glock cards refund. I would still have 784 "Crossfire" Glock cards on-hand to level it up again if I choose to, but by downgrading, I essentially "lost" 400 "Crossfire" Glock cards.
Doing this would make level-downgrading an option someone wouldn't do on a fly.There's a benefit and a drawback to doing this, and this seems fair because the player would be sacrificing one thing for the other.
Suggestion 3
To be honest, I would reduce how many points are rewarded for keeping a Supply Crate active for 6 waves and compensate this with earning something related to the currently-active cards mechanic alongside the points.
For instance, if there are two Supply Crates on the map, and one is destroyed, but one remains active as the humans win the round, they would receive 100 points and a Draft Chest. If both supply crates survived, players would receive 250 points and a Mystical Chest. This makes rewards for keeping the Supply Crate alive more worthwhile than just rewarding points that would otherwise be burned through spending.
These are my thoughts. Simple list of suggestions, but worth a look.