OK I misunderstood.
When you said you wanted to do a single peice neck, I thought that the stock you had was think enough for you to do a cutout headstock on the bandsaw. In that case I would have avoided the truss rod, because I don't think that it would have made any adjustments, but now I see that you have a much thinner stock to work with, so yeah I would use one, and I would use a dual action at that.
One thing you can do to hide the glue at the scarf joint is to use a high contrast accent wood shim between your ebony.
Something like 1/16" maple or bloodwood.
It's a beautiful board man!