Found a workaround for the second keyboard/midi pad problem:
1) get MidiStroke (free) and install, set to turn at logon
2) set up all midi-pads/inputs so that they are recognized by MidiStroke, don't add keystrokes yet
3) give every scene in OBS a keystroke hotkey (ie. alt-shift-cmd-1 for scene 1, alt-shift-cmd-2 for scene 2, etc)
4) open Automator
5) make a new Service
6) select "no input" in "every app" at the top somewhere
7) double-click "execute AppleScript" on the left somewhere
8) add your script (tell application "OBS" activate end tell)
9) save as service called "OBS Activate"
10) open system prefs
11) go to keyboard
12) go to hotkeys
13) go to app-hotkeys
14) click the + button
15) under App select "all apps" (important, or else it won't work if you are in a different "app" than the Finder)
16) under Menu type "OBS Activate". Just that, nothing else.
17) give that mothers*cker a keystroke combo (ie. alt-shift-cmd-t)
18) in Midistroke give the first midi-pad/input two keystroke combos:
18a) first line the keystroke for "OBS Activate" (in this case "alt-shift-cmd-t")
18b) second line the keystroke for your first scene (in this case "alt-shift-cmd-1")
19) repeat this two keystroke combo lines mumbo jumbo for all scenes
20) win
Wrote these steps from memory, some commands are prolly named slightly different plus English is not my first tongue.