I thought about this a bit more and, in reality, the amount of english words used could probably be cut down to less than 1000, which would cut down to 1/400th

I thought about this a bit more and, in reality, the amount of english words used could probably be cut down to less than 1000, which would cut down to 1/400th of my original figure. So no, I don't think it's more secure against advanced dictionary attacks.