1.154 gravity is still really high. That has a potential 19%ish ABV. I have had no experience with 4632 but I know the sweet mead yeast from Wyeast is really finicky and hard to use. With high ABV meads it is better to start with a lower gravity like 1.100 at most and step feed honey after fermentation starts to get you where you want it.
If you are not going to split this batch the aerate/whip this must twice daily for another 3-4 days. A bent coat hanger chucked into a drill does wonders if you do not have a wine whip. Just a couple minutes of whipping at a time. It sounds like you added enough nutrients and PH balancer to bring the PH up a good bit. In this case if not going with a lower ABV by splitting then if after 4 days pass and still no activity/gravity drop then get some Lalvin K1v-1116 yeast. That is a killer mead yeast that is good for up to 18%ABV.
Make a starter with it by mixing it with a cup of water, 1/2tsp of yeast nutrient and a 1/2 cup of your mead must. After a couple hours it should be foaming up. After that add another 1/4 cup of mead must ever hour for another 3 hours. Then pitch that into the carboy and it should be vigorously fermenting within another 24-48 hours.
all 3 buffer pH in the same manner, though. None are really better in that respect.
