Your setCheckpoint.Asm script is not correct (I'd suggest to comment out the "TriggerScreen" line) to fix that issue.
Also for your restart...
You could try implementing a Game Over screen, with this tutorial: http://nesmakers.com/viewtopic.php?p=12881#p12881
This tutorial uses the checkpoints, when you lose a life your player respawns to the last checkpoint, when all lives lost, you go a Game Over screen.
Also for your restart...
You could try implementing a Game Over screen, with this tutorial: http://nesmakers.com/viewtopic.php?p=12881#p12881
This tutorial uses the checkpoints, when you lose a life your player respawns to the last checkpoint, when all lives lost, you go a Game Over screen.