The lower OG beer will allow you to pitch a tad lower but a good whipping with a whisk the day after pitching would help. Gently rousing by swirling the fermenter every day after that (if necessary, often not) and then once you are seeing the krausen drop raise the temp to 20-22C to get the last point or 2.
I wouldn't have bothered splitting the yeast, this strain can be happily top cropped.
Cheers Smurto! Would you ferment at 18c at the outset until the Krausen drops?