Strange on the F12 key thing, I usually use Q to access the quick-menu. W to access the phone and you can always press escape to cancel the phone menu. I've never had to use the F12 button.
You are saying that your game crashes frequently when you go from the map to home? I have never encountered that so I cannot help.
The Dizzy and Neala switch is strange too, the only thing I can think of is that you have not done the Dizzy babysitting scene yet and so it will always give you Dizzy. Alternatively, it might be that you have not unlocked the babysitting part of Neala yet and the game keeps sending you the 'default'. (Originally Dizzy was the only one with the babysit plot.)
And yes, I agree that the end part is a pain in the ass. I got stuck there too.
My best guide for the last bits:
All right for those stuck like me: The coffin seems useless.
Use X-ray vision in the upper right room to see the patrols. <--- this is where the key is.
Go to the right, get the crystal. Unsure if that glowy thing on the floor does anything.
Then go completely left, ignite every torch ot make the bats dissapear (unsure if this is necesarry)
Then get the demoness (I freed her, dunno what the other option does)
Go back to the middle room and go upper middle. Dodge the patrol (statues have sightcones too)
There's dominus, touch the ladies with hearts and don'tget hit.
Then you fight goap (if you so choose), Just walk around, he'll hop to your location. Everyime he hits torches go out. When he has a teardrop next to him, send neala in with Q (first option).
Do this a few times and he sends in goons, just dodge them. Then he sends succubi to Neala, get Goap to jump on the succubi by standing next to them.
Then rocks fall, then more enemies show up until eventually he dies.