So your meter reads OL or infinity on both pin 5 & 6 of connector 30B with the 4 bulbs removed. Correct
Earlier you did use the words "is a bit too technical for me" so read through this and see if this is something you want to handle. If you don't, I can understand.
I am using Genuine HD year specific documentation on this problem but I think there is a type-o within it because some of it appears to be incorrect,
but that's OK. We can work through it without any problem. But because I can't fully trust the documentation, we have to play it safe. There is a spare 15 amp mini fuse in the fuse panel. Take it to an auto parts store and get a couple of those same shape fuses but just in a 5 amp rating.
Once you have a few 5 amp fuses, take the following steps.
The 4 bulbs are still all removed and connector 21A-21B is still disconnected. 30A-30B is also apart. With the Ignition switch ON, take your volt meter and measure the voltage on Pin #1 of connector 30B (harness side of TSM a brown/gray wire). You should read 12 volts.it didn't read 12, it read 10.58, but was continually dropping...not sure why, but I continued Now measure the voltage on PIN #2 which is a gray wire. You should also read 12 volts on it. same thing here, it was a little short of 12 and dropping....i continued though
If you don't read 12 volts on both, stop and reply. If you read 12 volts on both Pin #1 & #2 continue thought i was close enough and i've always read 12 on these so i continued....had to test this
With the key OFF, replace the 15 amp fuse labeled "Battery" with a 5 amp fuse. Install both right side and left side FRONT bulbs only. Make up 3 short pieces of wire with stripped ends. Connector 30B should be the female side. Insert one of the 3 wires you made into female receptacle pin #1,, another in receptacle pin #5 and another in receptacle #6.
*Pin #1 is always battery HOT even with the key off. So don't let that wire touch ground or you will see sparks.*
With key OFF, touch wire #1 to wire #5. The left front bulb should glow.
Now touch wire#1 to wire #6. Right front bulb should glow. yes they glowed exactly as you described
Install both rear bulbs.
Touch wire #1 to #5. Both left bulbs should glow.
Now touch wire#1 to wire #6. Both right bulbs should glow. again...exactly as described, all 4 glowed when their wires were touched
Reconnect 21A to 21B.
Touch wire #1 to #5. The BOTH left bulbs should glow along with the left dash indicator. right on again....
Now touch wire#1 to wire #6. Both right bulbs should glow along with the right dash indicator.and...yes exactly as described
Does all of this happen without blowing the 5 amp fuse..