Marine Salt, yes.
1.014SG, no.
9.0pH sounds way too high. 8.0ph should suffice and will be aquired strictly through the use of marine salt. No crushed coral sand or arganite required.
Brackish water could be classified as anything between 1.001SG-1.017SG(seeing that FOWLR tanks are usually 1.018). I would first start buy buying a bag of marine salt and mixing it to 1.005SG. Measure using a hydrometer because reguardless of what a lot of internet sources say you can't just add 1tbsp per gallon. The reason is that when marine salt is exposed to the atmosphere it starts to absorb moisture and expand... this is why the tablespoon method is inaccurate.
1.005SG is a good start for pretty much any brackish tank because chances are the brackish fish you purchase from the LFS will have been kept in freshwater for quite a while. Brackish water fish can be acclimated into higher or lower salinities rather quickly(over the course of a couple hours) but it will take you less time to acclimate it into 1.005(usually 20-30 minutes if not right away. It's better to take your time for caution sake).
You can't raise or lower your Specific Gravity more than .002SG over a course of 1 weeks time. Although your fish can handle it, and even enjoy it, your biological filter can't take a hard hit like that. You need to raise the SG gradually. What I do is when I do an approximate 25% water change, I change it with water that is .004SG more or less than the water in the tank. Also remember that evaporation will cause your Specific Gravity to raise so you need to keep an eye on that. I'd change it .002 more that what it was at the last water change rather that right before the change.
Tgere are 2 species of "Freshwater Morays" that are sold in the aquarium trade. They are Gymnothorax Tile and Gymnothorax Polyuranodon. I'd pretty much count on only finding G. Tile because G. Polyuranodon is very rarely avaliable. G. Tile should be treated like all other morays by providing it with a complex enviornment with lots of hiding places. As G. Tile matures it will prefer to be kept in high-range brackish to full marine. This is where the 1.014SG that SerLunchbox suggested will come into play.
If it were me I'd start the tank at 1.005SG, acclimate the moray into 1.010SG and leave the salinity in that area for a while and increase the salinity as your eel matures. Definetly plan to go full marine in your future, although high-range brackish would probably be sufficient for many many years. You'll be able to tell by your eel's health if it's satisfied with the provided salinity. However don't count on tankmates.. at least ones that will fit in the eels mouth.
