Well, guess your revisionist history cherry picks.  We did not even have a sacrament of marriage until the 12th century - at the earliest.  (yes, hermeneutic of continuity)
Trent clarified the marriage/sacramental practices of that day - more changes.
Again, you cite that you used Kaspar's book - that's your only evidence?  And then you condemn that book citing what - his name alone?
You would have trouble passing a high school history class working on analysis, evidence, theories, proofs, etc.
No, the church has NOT maintained the inadmissability of second marriages - and too often, the next *evidence* will be someone misquoting and mis-interpreting one or two scripture references taken out of context and interpreted *literally*
Spare us!!