Have you checked the starter relay?
I have read your Problem again, if the Motor is worm, Fan is working, the power is not 12V, the solonoid could be the problem, i have revisited compled the Starter an Alternator, problem disapear.
Please check also your coil, if he has 1,5 or 3 Ohms, if coil is damage your starting fire is bad.
You have CVH injection or with Weber?
I have now problem with the ignition!
