Barricade:

If you're looking to gain muscle, mass you have to eat quite a bit more than you normally would.  Building muscle takes a lot of energy, and your body doesn't like to do it unless you're in a consistent energy surplus since muscle is metabolically expensive to have around.

I personally find it impossible to gain weight on any sort of IF regimen.  Period, end of sentence.  I don't think 12 hours counts as IF -- but if you're really looking to bulk you'll have to consume far more than 3000 kcal!

Note: this doesn't mean to hork down loads of junk IIFYM...you'll just gain a bunch of fat.  Continue to eat like a predator, but more of it, making sure you're getting plenty of complete protein (1g/pound if your'e Oly lifting frequently).  This will be difficult, as you'll have to eat past your natural appetite.

And there's nothing wrong with a small scoop of whey protein immediately PWO, because that's your major anabolic window and whey absorbs VERY quickly.  I only use the NOW brand unflavored whey isolate, because once it tastes like a blueberry donut you have no idea what's being hidden inside (usually a bunch of junk carbs for filler).  Whey protein isn't fattening (in fact, it's slimming)...it's all the crap fillers that it's cut with (because real whey is expensive) that can be fattening!  Again, it's not a meal replacement, but I strongly recommend it immediately PWO to tide you over until you can fix real food.

I'm not a fan of peanut butter before bed because, as you said, it's incomplete.  If you're really trying hard to gain, just eat closer to bedtime, or eat another small meal right before bedtime.  

Like I said, if you want to gain more mass than you have now, you'll have to eat more than you do now!  Jim Steel once told me "Eat your way through sticking points", and it's true.

(Note to spectators: this is not recommended unless you are lifting heavy weights and trying to gain muscle mass!)

JS