Nokowi's video here shows the extent deception covers things. You won't even need the blindness procs, but they won't hurt. Heck, since you have Rebellion, you can always swap it in if fortification is an issue. (Am jealous, I do not have that blade.)
I am not sure either about sneak attack. I am curious myself, but adding another 70 or 80 damage on sneak attacks (along with the proper gearing to bring them about) should be solid. That is why I thought you might go halfling, since you could adding another 3d6. Do you have an Avithoul Seal? That really covers both sneak attack damage as well as insightful sneak attack and improved deception. You will also get venomed blades from assassin tree which scale 200% with melee power.
The elven spot trap enhancement seems to require
both a high active spot as well as search to work (someone had posted this a while ago in a thread, not sure which). So you would need very good gear constantly equipped to make it worthwhile (e.g. like Tharne's Goggles that have both at +15. I do not have those either...)
You will be ap starved so not sure if you will really want the elf tree if it is not giving you anything else. Shadar Kai will give you gloom stalker, which is like deception, and it begins with a rogue level (no bonus feat though). That line will also give more sneak attack die and some other nice buffs. It is just hard to fit all these things in since you will be AP starved.
"While sneaking, your melee weapons gain the ability to envelop their targets in darkness, making them briefly vulnerable to sneak attacks. Your weapons also have a chance to blind their targets for a short time."
Yes, the Twilight Blade will go the old way via avoidance--hi AC, dodge, incorporeality and displacement as well as improved evasion. There is a lot of good gear to cover PRR now and I could always jump into Earth stance or twist some extra, if need be. Stealth is also about avoiding fights, so that is a factor also.