Yeah, I manage to do consistent progress. I'm still tired after the GlobalGame Jam during which I gave a little help to a team.

Once the physics are done, first thing is the have a loop: die and retry!

So Moonie (yes I've decided that's the name of the character) can now take one hit and he will die on the second. If he touched a Checkpoint, he will be respawaned at that Checkpoint.

I also found a way to always spawn at the last activated checkpoint. 

Basically, when the player touches a checkpoint, he stores the checkpoint's coordinates.
When they touches a Checkpoint, I check if the saved coordinates matches those of that checkpoint. If yes then this Checkpoint is the activated one. If not, then the coordinates are overwritten by those of the new Checkpoint.

It's simple really, and I am happy with that solution as it works perfectly! Yay!