You're in for a very bitter beer. Scraping the top of the boil isn't going to reduce the bitterness of the kits, and the galaxy + magnum additions are going to give you something like another 60 IBU. I'd consider turning the stove off now.
Thanks for the advice! Went and had a taste at the 50 minute mark, and yeah it was pretty bitter. That's what I was going for so rather than risk going crazy by adding the magnum, I just turned off, threw in the crystal, whirlpooled it and then let it sit for 10 minutes.
I've now filtered into the fermenter and topped up to 23 litres. Had a taste and still bitter but much closer to what I was going for. Thanks so much for stopping me from making a total hopped up disaster
Waiting for it to cool before pitching a yeast starter.
EDIT: Take a reading and got 1.085, seems very high. Is OG affected by temperature?
Thanks,