Sorry, I found your message a bit difficult to read with no breaks in it so I hope I have understood it correctly. Also, the transcripts are over four disks covering the whole of Rutland, with separate files within each for baptisms, marriages & burials, so there is an awful lot of information for the surname Allen & variations. Anyway, here's what I've found:
Henry christened 18 May 1745 in Uppingham,Rutlandshire. Didn't find a 1755 burial. Possible marriage at Uppingham 28 Dec 1769 (as Allin) to Elizabeth Harding by Licence, both OTP. However, there was also a Henry Allen who married Bridgett Miller in 1755, Uppingham, also by Licence, so this could possibly be a second marriage, although I haven't found a burial for Bridgett so possibly not. Burial for Henry Allin aged 45 on 11 Feb 1790, Uppingham.
Mary christened 25 October 1746 in Uppingham, Rutlandshire. No trace of a 1756 burial. Possible marriage at Uppingham 25 Aug 1768 to John West, a Cooper. Both OTP, by Licence.
John christened 29 April 1748. I'm not sure what you're after here? If he was definitely married to a Mary then there are two possibilities: 5 Jan 1767 at Bisbrook to Mary Green after Banns, both OTP, or Nov 1768 at Lyddington to Mary Sumpter of Thorp/Seaton, by Licence. There are burials for both couples in both parishes.
William christened 15 August 1749. Didn't find a 1759 burial. Possible marriage 30 Oct 1775 at Belton to Mary Cotton of Houghton, Leicestershire, by Licence.
Catherine christened 15 March 1750. Transcribed as Catharina. No other information found so I will check the disks again later.
Susannah christened 30 November 1752. Didn't find a 1762 burial or a likely marriage (one in 1771 in Great Casterton looks like a different Susannah). Will check again later.
Haven't found a marriage for Henry & Elizabeth yet, but this looks like their burials:
23 Jan 1754 at Uppingham – Elizabeth wife of Henry (no age given)
28 May 1767 at Uppingham – Henry aged 67. Died of Smallpox.
If Henry was born c1700 and Henry 1745 was his first child, then he seems to have married late?