Time is moving slowly to the observer on the ship only when observed by someone on the ground. To the observer on the ship, time is moving slowly on the ground, but normally on the ship. The observations of the ground and ship based observers are equivalent. (This only applies to an observer on the ship looking at a ground-based clock. If the ship completes a round trip, the ship observer will find that more time has passed on the ground than on the ship. This is because the ship is no longer treatable as an inertial reference frame if a round trip occurs, there must have been some acceleration of the ship.) This is a consequence of the fact that both observers are equally justified in regarding their reference frame as stationary and the other as moving at near light speed. Therefore, the light beam would appear identical if you observed it from the ship as it does when you observe it from the ground, namely it would be travelling at the speed of light in both reference frames. The time dilation and space contraction effects are a consequence of this fact.
Right. Understood. I'm still not fully resolved over the issues discussed in post 160.