I know that the FD clusters have electrical issues, its normally just the speedo though
I have heard that so maybe this issue is separate from the rest.
Will try fitting new speedo soon and hopefully that will be one issue off the list! Its the oil pressure thing thats really worrying.
Your problem is 99% an earth fault and most likely with the speedo cluster, try changing the whole instrument cluster first then if it still persists check your earth connections from the cluster.
My money is on new cluster = no problem
As far as the oil pressure gauge goes, my needle is regularly reading zero. The original sensors were all .... tbh, as long as you check the dipstick regularly you will be ok!