The 150 W heat lamp is likely increasing the temperature enough, but you will have to measure it.
It is not a problem that the heat lamp is positioned behind the
UVB light. I do the same: towards the front is the UVB, behind is the heat lamp (I have two heat lamps as I have already an adult bearded dragon with a larger sized tank).
For the tube: The fixture comes with a 5.0. This has lower UV and is more for e.g. rainforest species. For desert species like the bearded dragon, a 10.0 is strongly recommended. If it's not available at the pet store, you can use the 5.0 for now and order the 10.0. It's easy to distinguish as the package shows a bearded dragon and it says "10.0 Desert".