On mine, the head end of the pressure plate has a ‘wing’ on each side that can be pushed in to release from the other metal enclosure that has not been removed yet.

you are moving the card from the left to the right.

I WASN’T moving left to right.

wedge it into the gap between the upper and lower cases as shown

You should clarify that in your second picture the image is taken looking DOWN into the device.

You are taking a lid off. Every picture of the inside like that will be looking down. Also obvious from the description, and the hardware pictured inside.

No idea on the internal bus. Not my area of expertise.

3 x 13.5 mm screws are actually TWO different types! Return to EXACT SAME HOLES.

-I discovered this on my mid-2010, but from comments, sounds like it may affect other models as well

2 x 13.5 mm screws are pointed ends

1 x 13.5 mm screw is a FLAT end <- CORNER HOLE

These areTWO slightly different lengths, and must return to correct holes. If you put the flat end screw in the wrong hole, it will stick out slightly. If you put either of the pointed screws in the wrong hole, they will go in all the way, but will not catch threads, and will simply fall out when laptop is flipped back over.

install it on the new drive

mid 2010 A1297. This is NOT HERE. Skip Step 14-15.

Step 16 ((NEW)) (unless I am crazy, this was not detailed). After removing original drive, remove bracket (2 screws) from its side, and reuse on new drive. If you are confused which bracket, the drive is held in place with 3 screws. The 3rd screw on the center of the logic board side, goes through this bracket that you need to reuse. Top view of bracket can also be seen in Step 11 picture.

mid 2010 A1297 again. Different configuration. I had a black plastic housing along this whole side. The large flat ribbon connects to it and I LEFT THE RIBBON IN PLACE on this housing. I removed 3 screws here to allow this black housing to be lifted off the drive and to the side, along with the camera line (held down by 3rd screw). When REPLACING this black housing after installation is complete, note there is a small tab on the disc slot side of the housing that needs to be inserted into a slot for correct placement. Then SKIP TO STEP 10 on this IFIXIT tutorial.

Again, also mid 2010 A1297, the large flat cable crosses the drive. Remove on logic board end by prying carefully "UP" away from the board. Step 8 here: (http://www.shareyourrepair.com/2014/11/h...)

My mid2010 1297 was also different. Camera cable is per "step 7" here (http://www.shareyourrepair.com/2014/11/h...). Very very delicate.