That “riser” thing is generic, you can transfer from any iPads. What you also need is a rubber gasket which doesn’t usually come with replacement home button iPad 5/6/Air 2/mini 4 Home Button Gasket You can get it cheaper elsewhere, or use salvaged ones with right cut-out
You can use heat gun to remove that sensor, but in order to solder onto the replacement screen, you need to use a soldering iron. Some companies sell replacement screen assembly with sleep/wake sensor pre-installed, see if you can return bought screen for a full refund and buy one with installed sensor from companies like MobileSentrix and InjuredGadgets.
In order to retain touch ID functionality, you need to salvage original home button from broken screen and transfer to the new one. Buy a replacement screen with daughterboard pre-installed (‘the middle flex’ circled in picture) to save yourself the hassle of soldering, from any reputable vendors like iFixit and MobileSentrix. Follow this guide for disassembly of device: iPad Pro 12.9" Display Assembly Replacement Follow @refectio guideline in his answer to this post for re-assembly: After doing my repairs (battery and screen) I have problems
You may have inadvertently damaged digitizer connector on the logic board, judging from this picture A caveat for replacing screen on 12.9” iPad Pro is to always make sure connectors are aligned before pushing them in, otherwise you’ll end up with broken connectors on logic board and/or screen flex which requires micro-soldering to fix = more $ As for the home button, you should release the lock mechanism first and then pull out the cable (piece of plastic on the left of home button connector, flip it upward to release).