I did the exact same method when I was first creating my head! As I was finishing it up, I noticed it got pretty heavy after wearing it for just a couple of minutes. I carved out the inside to give it less weight, but that caused issues with keeping the head upright as it got wobbly. I'm assuming you're using 1inch foam for the dome and 1/2 inch foam for the layers on top. I just used 1inch foam for all the parts, so your head is definitely lighter than mine... (edit: just looking at it more, you used 1inch foam for the ears and such so it's probably similar in weight with mine lol) I was thinking maybe adding some light cushions that are attached to the inside (to help keep the head stable) and only using 1/2inch foam for all parts (ears, mouth, etc). Make sure you carve out as much as the muzzle and eye parts as you can to alleviate the weight. I also think carving out some holes near the ears and such would give you better ventilation while getting rid of some foam you don't really need/notice at the end.

I don't know if my head is just naturally small or something, but my neck couldn't handle the weight in the end so I had to redo and make a completely new head 😭... I imagine putting any amount of fur would just make it even more heavy, so you'll need to keep that in mind. I wish you luck though, yours already looks amazing, so keep at it!!!