Where to start?

Download a copy of the Volvo D jet trouble shooting manual. You should read through all of it; but, a good place to start is with the procedure for setting the idle speed and the throttle switch (throttle stop screw). The throttle stop screw is not used to set idle speed. The stop screw and throttle switch have to be set exactly as described in the manual for the engine to idle with a steady speed.

If you broke the connections to the temperature sensor near the thermostat I assume the two hoses that you have been fiddling with are the auxiliary air regulator connection hoses. If the aux air regulator doesn't work and has been blanked off then the hoses don't really matter unless you plan to replace or rebuild the aux air regulator. With no aux air regulator you need to cap off the two ports on the intake manifold that connect to the regulator. The two ports are just under the manifold directly below the throttle plate. If those two ports are not blocked off then you have unrestricted air flow into the manifold which will cause a really high idle speedd. With the two ports blocked off you can set hot idle speed using the idle speed setting screw. When the engine is cold this will not admit enough air to keep the engine running so you you will have to press down on the gas peddle just a little bit to keep the engine running until it is warm. The only alternative to this is repair the aux air regulator or find a used one that works.

I don't understand the reference to the crankcase hose going before the butterfly. The PCV hose from the oil filler cap goes to the restricted nipple on the intake manifold as shown in this photo
https://www.swedespeed.com/threads/what-another-142-project-car.201780/post-5163041

The hose from the oil separator on the side of the engine block typically feeds into the bottom of the air filter housing (if you have a stock air filter).

I don't know anything about the injectors that you received from VP Auto. I do know that the Beck Arnley 158-0438 injectors are exact fit drop in replacements for the OEM Bosch 280-150-036 injectors. I use the Becks and there are now a number of 1800E owners running them without issue. With the Beck injectors if you set your fuel rail pressure to 30 psi the D jet system will operate as intended. With your mystery injectors and low fuel pressure you are kind of off in no-mans land. If you don't want to fork over the roughly $65 for each new Beck injector, send one of your injectors to a fuel injector testing service to get the flow measured. At 43.5 psi the Bosch will flow around 580 ml/min. If your replacement injectors are close to that then the engine should work with a rail pressure of 30 psi.

You can find parts or acceptable substitutes if you look hard enough. Some parts have a very nasty cost. However, I don't think you can find new auxiliary air valves; but, there is somebody offering a rebuild service. Your best starting place for parts is Eric / Planetman at High Performance Auto