I've never had an issue with Splenda, but everybody reacts differently. There are some people that will come out of Keto after drinking a diet Coke! That has to suck.
I eat almonds and peanut butter while low-carbin', you just have to keep the serving size down. Also, the peanut butter I eat has less carbs than most (and more protein) - Naturally More - What Peanut Butter Should Be (you can find it at Wal-Mart).
Lastly, these will help you stay low carb AND get a ton of fiber in -