Hi, with the size of the clearances door to frame, your seals are ineffective & not compliant. There is seals you can add that are tested for fire doors such as bats wing seal for smoke and acoustics there is a large choice of manufacturers such as lorient, norseal etc, they are self adhesive & fit in the rebate/doorstop. The gap at the thresh, you require an auto drop down seal, which come in face fixed or concealed (the concealed would require a tradesman to install). Your closer , you said you adjusted controls but the door would not fully close, check that the door is not binding on the door stop/rebate when closing. When adjusting controls only turn quarter turns at a time and adjust the speed first before you adjust latch control. You mention door is heavy to open, it is possible the power setting of closer is on incorrect setting , this is adjustable, but I see no photo of the closer.
I hope this helps
Regards George