Hello Nathan, your Alexander Bonny was the half brother of my 5x great grandfather Robert Bonny, so we are related from their father Alexander Bonny born 1699.
Your Alexander was baptised 21.2.1743 at Ulcombe in Kent and as you say he married Susannah Boorman in 1767.
I have traced the line going back to Christopher Bonny who died in May 1598 at Boughton Malherbe, Kent (Lenham), source his Will. Our line then descends through:
Thomas bap.9.2.1589 Lenham
Alexander bap 10.5.1632 East Sutton, (a Clothier) Will and Inventory available.
Matthew bap. 25.12.1671 East Sutton
Alexander bap. 17.12.1699, Will and off the top of my head, i think there is an inventory (will have to check in my file.
I did all this research back in the late 90s, but have had the file out lately as I have often wondered where the family originate from. I suspect they may have been Walloons who came here in the 16th century. Bone (which is a variation of course of the name) is a French name. Having said that, I have just found a reference for a Bonny will in Lenham from 1469, so that is probably my theory out of the window.
I could let you have copies of my research if you wish. The Wills and Inventories provide a fascinating insight to the family.