The information below from "Oxford University Alumni, 1500-1886", in connection with birth of first child, lends an estimable timing for his first marriage:
"Walker, Augustine, of Bucks, pleb. New Coll[ege], matric. entry under date 22 Dec. 1576, aged 18, scholar 1576, B.A. 30 April 1580, M.A. 17 Jan., 1583-4. Of the city of London, clerk, licenced 5 June, 1591, to marry Barbara, daughter of Thomas Wykyn, of St. Ethelburgh, London; rector of Ilmington, co. Warwick, 1586-1632. See London Marriage Licences, ed. Foster." — https://www.ancestry.com/imageviewer/collections/8942/images/RDUK15...
The later part of Overview appears to be repeating his Will.