You should have pulses of fuel at the injector end, not just drops. I'd start easy and work toward hard. So, change the fuel filter, then bleed the system. Make sure the fuel is fresh. Then check your fuel delivery to the injectors and see if it looks better when cranking. If the machine has sat for awhile, a plugged fuel system is vastly more likely than losing compression spontaneously.
Did you check all the injector lines for fuel delivery?
If you already have access to a compression tester go ahead and try it, but I don't know what the specification for that engine should be, and it's unlikely you have a service manual. If you have to buy one, you may find the adapters won't fit. For example, the kit sold at Harbor Freight doesn't fit Yanmar machines, even though it has several adapters.
A compression release would be a lever or cable going through the valve cover somehow.
It will get resolved, keep after it! Just go about things methodically and with a logical plan, rather than throwing money at the problem and hoping. If the compression test reveals good compression, we're back to a fueling issue, and you'll need to replace the fuel filter and bleed the system. If it reveals low compression and you rebuild it, you will replace the fuel filter and bleed the system. From my end, it makes sense to do the things that will get done anyway first.
