I do not think you screwed up. It's just time to start making adjustments.

I feel it's important for me to have a 5 lbs buffer. I don't stress over the buffer, I accept it. I think it takes a lot of mental adjustment to do that.

I was VERY thin for years but I never weighed the same constantly, I always wavered from 5 lbs above to 5 lbs below my "normal" weight.

So the first thing I suggest is coming to terms with that 5 lbs. You have the tools behind you to know how to take those 5 lbs off and not let it get out of control.

As far as raising your carb level for maintaining. You say you gain whenever you eat higher carb foods. Are you eating those higher carbs in bulk? A whole dinner followed by dessert? Can you attribute a gain to certain foods?

I really suggest people, even at goal but want to raise their carb level, start again with OWL. Raise your carbs in 5 carb increments and follow the ladder. I believe it helps in more structured eating, you learn more what foods your body can handle. Even if a food is included in the ladder, such as nuts, does not mean every person can eat them without a gain. Everyone is individual and we each have individual sensitivities to foods.

If you start getting bored with the whole 5 carb thing and are doing fine, bump them up by 10 at a time.

By doing it slowly, your body will slowly start adjusting to the added carbs and accepting the added carbs without a gain.