1: The estimated time, assuming GR, is 85 million years. GBD and similar theories, however, predict a gravitational-dipole contribution, which will speed it up, though how much depends on the theories' fudge factors (GBD can be made arbitrarily close to GR).

2: Very likely; that possibility is being actively investigated. In some simulations, the coalescing neutron stars' temperatures go up to several MeV, which means gamma-ray luminosity.