I’m not sure how much I can help but let me try. Some of the grounds with small ring connectors probably are attached to studs on the back of the trim strips at the bottom of the dash. There are likely other grounds at the angle pieces at either end of the dash. What I’m not sure of is where they are attached to the “real” ground. A simple wire could connect the frame to the trim strip would do it but I don’t think that’s it.
As for making the dash easier to take out, I have heard of some people who isolated all the dash wiring attaching them to the dash with a plug to go from the dash wiring to the rest of the loom. Then, theoretically, you unplug the dash wiring disconnect mechanical gauges and heater controls and unbolt the dash.
It ic certainly is possible to take the dash off with the windshield in place. Taking out the crash pad is a different story.
Does that help at all?