Firstly I would avoid doing unnecessary and expensive work and just concentrate on the problem at hand.

Does it turn over at full speed or is it turning over slowly?

Have you tried the jump start trick yet? Did it turn over quicker?

Have you had the battery and alternator checked properly for charging capacity by an auto-electrician?

Are all belts in good condition and tensioned up correctly?

Are all electrical connections between the battery, chassis and engine secure and in good condition?

That should clear the electrical system..............

When was the last plug/coil/lead change?

Can you get the fuel pressure measured properly? This should include a bleed back check.

Fuel filter last changed when?

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