Electrical storm problems

i bought some new ones to update. god only knows how long thy've been there (but working fine). getting the darn things out is virtually impossible! a couple of them has little switch-like things on the side, which made it easy. most don't. :( also, i'm having the same trouble getting the new ones in! they just don't want to turn. can anyone help? many thanks, paula.

Sorry for the length of the post, I appreciate replies from experts and others willing to read the whole thing. I recently moved to a charming cape cod built in 1942. My first project was to hang a ceiling fan in a bedroom, and as I took out the old light and checked out the support for the box, I noticed that just moving the wires around a little, the sheathing covering them kind of peeled away like string. I was left with bare metal, copper on the inside with a coating of gray metal, (must be a World War II conservation thing). I suppose this stuff is fine if it never gets moved. I also found that almost all of the lights and outlets are on only three circuits, since 60 years ago they weren't running all that much stuff. Other double breakers are used for stove, dryer, and a recently-removed room AC. So I decided to tackle one of the circuits and just replace it all with good ole' NM- B with ground. I was able to get to most of the boxes through the walls either from my unfinished basement or almost unfinished attic. A couple holes in walls were needed; those can be patched anyway. I'm about ready to connect the new wiring to the panel, which I've never done before, and figured I'd ask a couple of questions just to be sure I'm okay. (I've invested three days already, and dear wife is getting tired of half the house being out). Here are three questions, numbered for easy reference on replies: 1) Since I can't get inside the walls to attach the cable with staples next to the box, I just made sure they were snugly clamped in the 1940's style metal boxes. I could still staple where I went up or down through attic/basement. Is that good enough to secure them inside walls. 2) If I have three cables in a box with an outlet, can I use both the side-wire and back-wire (push in) terminals on the outlet. That way I won't have to connect with a wire nut and pig tail to the outlet. The boxes are not that big and I'm concerned about space and code requirements for items in each box. I really don't want the mess of brand new boxes. 3) Since I've never connected to a panel before, are their any tricks beyond what I've read in the normal handyman books? (I think Time-Life had a good description). I suppose I just turn ff the main breaker, change the new cable for the old through the same hole in the panel, and connect everything the same way it is now. I'll have a ground wire on the new cable, which the old didn't. I thought there would be a bus for the ground, but I see the newer grounded circuits terminating on the neutral bus bar. So I guess the neutral and ground are the same? Any other things I should think about before going live with this circuit? I'm fairly confident about my connections to switches, fixtures, and outlets, I've done them before and the books are helpful. The real pain was that 60 year old wires don't have nice little black, white, and red that are easy to distinguish, after disintegrating for half a century. Thanks.