For the second problem: i think 0.002 * time_step is too small. Take it higher f.E. 0.02 and play with the wait(10) or wait(15).
"Wait" above 1 frame will indeed slow the sky down but then movement of the sky dome will not be smooth at all. The higher I rise the value the more stuttering there is.
0.002 is fast because the UV range is from 0 to 1 in the engine.
I tried many numbers already, 0.02, 0.1, 0.2..., 1, 2, etc. However everything above 0,00x is ridiculously fast. The slowest number I found, was 0.002.
Or do you want to say that no matter what I chose between 0 and 1, it is going to be too fast in case of UV movement?