I would increase to 1.75 units tonight. With TR, if you are only seeing nadirs in the 200's, you increase after 6 cycles. Don't hold doses longer if they aren't giving you blues or greens, or you can get glucose toxicity setting in. Basically, his body is getting used to higher numbers and it'll take an even higher dose to break through.
Insulin is a hormone, not a drug. You don't increase and always see a corresponding improvement in numbers, until you get closer to that fitting dose.