Bend the arms. You're gonna make IK rigging it very difficult. You can separate the head for the retopology if you want. Depends on how flexible you want to show the head to be.
Hey, this looks quite cool already. The pose of the arms is almost ok as it is: palms facing downward and shoulders 45° down. You only need to bend the elbows forward just slightly as Brian said. This makes the setup of the IK much easier. Plus, deformation-wise, it's always better to not have a joint posed in the most…