It looks like you have a good handle on things.
Since you have a pH meter or strips - and are prepared to make any adjustments then you are good to go. I am betting that the dark malts and crystals will knock out most of the alkalinity. Without your salt additions, I am seeing about a 5.4 mash pH prediction so be prepared to should the mash pH fall below 5.2. Bru'n seems to predict just below 5.3.
With the alkalinity in your sparge, I would adjust it to just below 6.0 pH, which should require about about 3 ml - as you estimated.
Best of Luck!