I agree with the comment to not worry so much about getting some of the yeast over to your secondary and the need to top off to minimize oxygen diffusion into the wine. The rate of oxygen diffusion is proportional to the surface area exposed to air and the concentration of oxygen. So getting the level up in the neck of the gallon container will have a big impact in reducing oxygen diffusion.
If your kit does not contain kieselsol and chitosan and you want extremely clear wine add in some kieselsoI after you degass the wine. Wait a bit then add chitosan. My kit said wait 2 minutes for the pinot. This combination is phenominal in clearing wine. My pinot came out extremely clear by doing this.