The most effective way to heat up the glue is to leave the phone in full sun - if it's available. In fact I would always wait for a sunny day to repair any glued together Apple device. The heat will be very even and the phone was probably designed to survive anything the sun can throw at it - although it can get very warm. (I'm in the UK) If you leave the phone turned on it will give a warning if it goes near the temperature limit.

To soften the glue, I prefer to leave the iPad out in the sunshine - it gives it a really even temperature and is hot enough on a summer day. Once the glass is off I only removed 4 screws for the screen, 3 screws in step 65 and the single screw clamping down the battery. That is enough to prise up the battery clamp and slip out the battery from under it. I put talc on the replacement battery sticky strips since there's no way it is going to slide around in there. And I just cleaned up the old glue around the screen because there's more than enough left after opening it. I don't need it to be waterproof.

IMPORTANT: there’s a spring under the post which could go anywhere when the post comes out with the screw.

Only two screws as stated above need to be removed but as people have found out, the one in the cowling can bind into the post below it and it’s the post below that unscrews instead. So you end up with the screw+the post+the fan all together as one. That assembly can be worked out, and then with two pairs of pliers the post and screw can be separated.

The lower right T6 fan screw is a standoff (that also secures the logic board). This can be loosened and kept with the fan, or (since it is friction captured in a grommet on the fan), the fan can be lifted off, being careful not to dislodge the grommet.

The HDD Temp sensor is just a NPN transistor - in the past with SSDs I have used a 2N4401 - connect the grey wire to the emitter and the black wire to the other two pins. Works a treat.