Do these have the comfort waist elastic waistband?

These have a slightly elastic waistband. It is not the sliding-fit waistband.

Is this similar to the signature classic just with less cotton?

Yes ... the Signature Classic has 98% cotton and 2% elastic material (presumably the waist). These have around 60% cotton, 38% polyester, and 2% elastic. Those are by recollection but close enough to get the idea.

How's the room in the croth area? I have problems with them fitting tight.

I am a big guy and have found the pants fit perfectly. Adequate room in the crotch, but not excessive. I own 3 pair of these pants.

May be a silly question but how deep are the front pockets? I recently purchased some that had somewhat shallow pockets (maybe not genuine).

The pockets in the New Dockers pants are not as deep as my old pair. Its the same style and size. the new pair has pockets that are 10" deep (see picture) and my old pair has 12" deep pockets (see picture). Until the manufacturer fixes this I'm not buying anymore. This problem has been described in many reviews and still the manufacturer doesn't fix the problem. See pictures in my review