The first thing to do is to clarify some or all of the dates, with reference to the original documents.
Before 1752, New Years Day was 25 March, and this often causes confusion. For the period 25 March - 31 December, the year is the same whether in Old Style or New Style. A date between 1 January and 24 March would be in, say, 1724 Old Style, but 1725 New Style, and the best way to transcribe it is the unambiguous 1724/25. Unfortunately some databases seem not to accept dates in that format.
However, some transcriptions use Old Style without any conversion, and some convert it to New Style. No doubt some people seeing it in New Style without any explanation do a further conversion so it comes out a year later than it should.
In your case, where you say 'Copy held' does this mean you have a copy of the actual register, will etc, or just of someone's transcription? I think we need to be clear on this in order to work out what's going on, because even when the calendar change is taken into account, the dates you give don't make sense. The sequence you give is:
7 Nov 1745 - marriage
9 Mar 1745 - burial (1745/46 - appears to be in NBI as 1746)
14 May 1746 - will written
15 Jul 1746 - will proved
(And if the NBI was actually right about the burial and it was 1746/47, then the will would have been proved before he died.)
Is there somewhere we can see these documents online for ourselves? One possibility might be that a '5' has been mistranscribed as '6' (or vice versa).
