fire door slamming has loosened frame

My kitchen to garage fire door has always caused me problems by its constant slamming, previous owners obviously didnt care as the frame has become loose.
Now i have fixed three frame fixing bolts down the lock side of the jamb but still its loose, The problem i have is that its fixed to some very light breeze blocks, the ones you can push a screwdriver into.
The gap between the frame and the block is becoming bigger as bits of the block are falling off garage side.
whats the best way to cure this, i have tried covering the crack with smooth filler but its now falling off due to irregular slamming,
The crack varies from 2mm up to 4" in places,
Would a flexible foam filler solve the problem ???
Any ideas would be very welcome as the plasterboard, kitchen side is becoming loose now.
Regards

Remove the architrave if you have them, then break some of the celcon block just behind the door frame on both side then make good with sand/cement, make sure the cement is hard before usng the door again.
You can use door packing wedge shape but cement is better.

Cheers
What mix would be the strongest and most workable ??
No architrave , just a 2"frame fixed with wall bolts

1 part cement, 3 parts sand

just an update, tried the cement trick but due to wind tunnel type effects when garage and back door are open the cement just cracked and fell away.
I tried expanding foam and its done a cracking job, only thing i noticed was the frame was bowing out so i jammed a length of wood between the two uprights and its strong as anything thats really strong