If the car is cranking intermittently, the alarm system is less likely to be the culprit. Yes, relays do wear out with age and the starter relay could definitely be at fault. The clutch start switch or neutral start switch (depending on whether you have a manual or automatic transmission) is another likely source of the problem. I would start with testing these.
I would have to look at the wiring diagram for the alarm system to be certain, but I'm pretty sure the connector just needs to be unplugged so the alarm sees an open circuit and doesn't arm.. now if there is a fault in the control module it may prevent the alarms starter relay from closing. In that case, you would bypass the alarm starter relay and disconnect harness connection for the alarm module. I'm at work presently and it's going to be a late day here... I'll try to look at the wiring diagram tonight of tomorrow.
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