Large ac input class AB biasing
Taking hfe of 100 then Ib should be 5mA


That assumes that hFE remains constant at 100 and this is by no means the case when the transistors start to work harder and are delivering current to the load with a much smaller volt drop to the rail.

Take a look at the BD139/140 data sheet; with a current delivered of 0.5 amps and a volt drop of 2 volts between collector and emitter, the hFE can be as low as 25.

Also remember that the current of 0.35 amps you have calculated is only the load current - there could be another 100 mA flowing due to class AB biasing.

Fix the orientation of Q2 in the top diagram of your question please.