the 7 has 2 white dots on the shell that should line up with 2 holes in the charge port flex (near the connector end), this is so they line up, if you having problems getting them lined up then unstick the charge port flex off the shell and line the holes up with the dots, you may need to remove the loud speaker inorder to adjust the flex correctly. if you have messed about with the connector too much you may need another charge port flex or it will keep popping off.
first thing, try a hard reset. (press volume up, volume down, then hold power button until apple logo then release.) if this doesn't work then try reseating the vibrate connector, if that doesn't work then you may need to transfer the data from the old vibrate to the new one using a eprom data transfer tool. if that doesn't work then try a new vibrate and lastly a new charge port flex.
I suggest trying a new front cam, this may resolve the boot loop just not the home button. you could try reseating the home button flex`s and trying a new screen to fix the home button but I just maybe that the homebutton is broke.
I would try cleaning the SE of its water damage if it was done recent. Putting the damaged SE logic board in a different shell will probably achieve nothing (even if a 5s shell were compatable, which they would be but all the flex cables have different connectors apart from the screen and front cam.)
There are 3 possible parts that could be giving you issues, the black plastic square antenna at the top left, the flex at the top middle that connects near the rear camera, and one that connects next to the battery connector and goes over the loud speaker. For a guide on screw sizes do a google image search for iPhone 8 screw guide.