really the red key should never be in the igniton unless you are using it to program blue keys into the ecu. if the red key now shows the key code light at all times it would suggest the ecu is switched on and not recognising the red key, that is usually a sign of ecu damage i have seen more than once
the ecu is in the engine bay to the left of the battery when looking into the engine bay, its is a rectangular metal box with a big wiring plug attached to it.
the damaged relay sounds like a possiblity. electrical shorts often blow fuses and relays. it is definately worth trying, but im not aware of any relays on the inlet manifold and as i remember the wiring diagram for the coil shows no connection to any relays, just the ecu.
taking the car to a fiat specialist for a diagnosis may be the cheapest option, but getting the car there will be a stuggle if you live in the middle of no where, you can hardly tow yourself. a diagnostic check is usually £30-40, or possibly a bit more at a fiat dealer. if someone can help you get the car to a specialist it could save time and money. they will tell you if the ecu is damaged, and any half decent place will be able to identify a damaged relay causing the problem.
you must like fiats (and hassle) if you're second car is a punto. you say it has fuel going to the cylinders but no sparks. that could be a coil problem (yes another fiat coil problem!) or an ecu problem. it can also be a simple electrical problem such as dirty batterty terminals, a damaged main earth strap, a blown main fuse, dirty or corroded connections for the coil/ecu wiring. have you tried anything to fix the punto? can you provide any more info about the punto, maybe we can help?
you're in quite a pickle with 2 broken fiats stuck in the country side, i'd be willing to come and have a look at your cars if you live near me, im in co. durham (north east).