Sorry I forgot to let you folks know the results. The latest iteration of this porter worked very well. I got the salt just right--just 1.5 tsp at 10 minutes in the boil. Like a gose, the salt did not, in fact, inhibit the fermentation, and it blended with the dark malts really nicely. There was actually a peanut butter flavor that came through, likely due to the salinity/brine flavor melding with the chocolate undertones. It's great.
This actual beer was not bad, but there is still a lot of room for improvement. I think I need to make it stronger ABV-wise, and beef up the malty backbone. I dont like chewy porters, but I dont like them thin, either, and the salinity, while balanced this time, came through a little too strongly due to the thin malt. This has the potential to be a rather excellent peanut butter porter, or something like that.
Bottom Line: 1.5 tsp salt in the boil for 5 gallons.