engine problem Options

[STP]

So, My 914 has been sitting at my grandmother's house for the last 2 months and after finally being able to work on it again I've run into a few problems.

Firstly, none of my gauges are working. Not the tach, not the fuel gauge, nothing.

Second and more importantly, I was checking and adjusting the timing on the dizzy according to the PP article, and the engine started making this knocking noise. I'm not sure what it is. At first I thought it was preignition, Seeing as I advanced the timing, but it sounded mechanical, like lifters maybe but really loud. Then I thought because it hadn't been started in a while that maybe I should have primed the oil pump. But, like I say, I have no idea so far.

I did a compression test on it before I put it away and one of the cylinders was about 40psi lower than the others.

So my questions are:

What could the gauge problem be? I dont even know where to start so even that would be helpful.

What's the most likely answer to the knocking problem?

What do I do about the low compression? I thought 40psi was kinda high. Will I need to get a valve job? Could this be related to any of the other problems I'm having?

Compression:
140
120
120
100
I have a 73 2.0 with Webers (40s) if this helps.

Thanks for all your help, Sean