No, pre 1837 marriage entries only contain the names of two witnesses, not fathers' names, which was only a requirement following the introduction of civil registration. I would find out from the Bottisham transcript who the witnesses were to Isaac's first marriage to see if they provide a clue - they might be siblings**.
I suspect he may have been a son of William and Mary, but proving it is another matter. I think I would be looking to see if the Lode Baptist church book was available - it is - Bottisham Lode Strict Baptist Chapel - at Cambridge Records Office. I have transcriptions of similar Strict Baptist chapels in Beds, and they contain lists of church members. You might get lucky.
Was William of William & Mary really dead by the time of Isaac's second marriage? If he wasn't it might imply that his father was either another William or fictitious
David
** I see you were given these names on your earlier thread. No Cornwells among them, so not a lot of help. Another door closes.
