Sorry to have not answered before, but we have no experience ourselves or from other clients with your problem. I'll make some suggestions based on your questions.
Where you press the Ctrl key will stop the sweep for the word placed with the last Spacebar. The color sweep time will be from the Spacebar press to the Ctrl press. You should press Ctrl where the singer should stop singing, which will pause the sweeping until the next Spacebar press.
There is no "prefer" page layout. The 4 lines are "drawn", whether you use them or not. Using fewer lines will draw faster than all 4 because there is less to be drawn.
When you use * to split words, you must tap each portion in with a Spacebar press. If you aren't aware of this, your second word portion (following the *) will be placed with the next Spacebar press. If you think that press is for the next word, you are wrong. That can explain the sweep color not following the music as you might think. I would not use the * until you are quite proficient on just placing whole words. Then, you will know when you are not placing *-split words correctly.
As to the last word not sweeping at all, I have no explanation. We have never seen or heard of this before that I can remember. I expect it might be a Ctrl press was entered without realizing it. However, the next Spacebar press would have placed the last word, which would still sweep it.
Do you still have these problems? If so, it might be beneficial for us to get your song music and lyrics and try it here to see what we generate. Let me know.