Any recommendations for the best resources for in-depth study of Aquinas on Lombard's Sentences?
Sorry, no idea, but Lombard is another book we really should have in Logos. If you suggest it in the Suggestions forum I'll go vote for it.
http://www.vaxxine.com/hyoomik/aquinas/sent1.html
is the only place that I know ... but then again it is outside my area of expertise.