Hello I'm Neal and I am here to help resolve your issue. If I cannot help I will opt out and refer your question to another expert.
It should not be the ignition switch since the ecm is getting the signal, since you have ruled out the starter, it pretty much has to be the ecm that is the issue. It should be engaging the starter until the engine is running, it must be misinterpreting the input and it thinks the engine has started. Since it is trying to start I don't think it is getting a false signal and it must be in the ecm itself.
i can jump the relay and make it turn over just fine. i agree i bet the ecM is the problem. i will see what i can do tomarrow. though it will sometimes crank up normal and other times it just does that.