I think you are not far away on Sepia , for Venetian Red I would use Light Red or Indian Red and not worry too much.
The main thing is please yourself don't get too wound up about what "you should be doing"
jviguers, when looking for substitute colours, or how to match something, the real question is what you're seeking to do - if you only need a colour because it's part of a mixture often something similar will do just fine. With experience you can substitute very different things and just tweak the mix appropriately to compensate (adding a little white, a touch of black, a dot more red etc.)