What caught my attention was the part about the starter struggling against the compression. If it were me I would try the free stuff first - clean the throttle body and try the fuel pressure experiment. Then move on to other, more costly, stuff. The jumping tach needle is interesting. Have you scanned the OBD for fault codes?
How old is the battery? How much is the voltage dropping when you crank the engine? What’s the voltage just after starting and it’s running rough?
Sorry for all the questions. Just trying to cook up some food for thought.
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