You should really consider Juri Anikejev's suggestion. The King must land immediately behind the last captured piece, provided (1) that it is a King and (2) it's a multiple capture sequence. This means that three Kings will win against a lone King. Note that, unlike in Killer Draughts, the halt rule is not valid at single piece capture.
You seem to assume that the source of the draw problem is that three kings cannot win in general against one. Unfortunately, this doesn't seem to be the case. I made a quick change in Scan's move generator and it appears that, at least at that level, the draw rate in Killer-light is still extremely large.
I will try your proposal for backward captures. There is also the possibility that I made a mistake; I will keep you posted.