I had CMP inspect and slug it so I am hoping they were able to measure it correctly. I am planning on only shooting black powder out of it. They said it swallowed a no-go and field gauge, so I am leaving the smokeless powder alone. While they wouldn't agree or deny they said I SHOULD be ok shooting black powder loads out of it.
I am going to give you the Company answer: Don't shoot it. You have a rifle that is known to be out of mechanical tolerance. The risk is that with excessive case head protrusion, you could have a burst case head.
These pictures came from Chinn's Machine Gun book, Vol IV. You should read the section on blowback to understand the concept of case head support.
The distances in this diagram relate to 20mm cannon shells, not 45/70 cases.
What may mitigate your problem is the construction of modern cases. Originally your Trapdoor fired balloon head cases which were very weak in the case head compared to modern cases. Modern cases are solid head cases with thicker sidewalls. But, I don't have any measurements nor analysis to determine just how much a modern case head can protrude from the chamber and not burst at blackpowder pressures. Nor have you provided any measurements about just how much headspace you have. Here is an excellent post on balloon head cases and headspace in Martini's.
Word of caution about balloon head cases
http://forums.gunboards.com/showthread.php?787-Word-of-caution-about-balloon-head-cases
You do not know the previous history of your rifle, it is altogether possible that the headspace is as it was when it was built or rebuilt. Or the headspace has grown due to previous owners shooting loads that were too high for the metallurgy of the period.
So, the company answer is don't shoot it. You have to decide for yourself what to do. If you do fire it, monitor the condition of the cases, see if there is any unreasonable expansion of the case heads, and always wear your shooting glasses!