You've answered Duboman's question. You are not mashing those grains. You are steeping them.
There is no base grain in there to give you the diastatic power you need to convert the starches to sugar. You are only getting color and flavor from steeping those grains. I suppose you may extract some starches which could contribute to gravity, but you're not going to get much if anything.
If you want to mash, you'll need to include some base grains and hold the temp for 60 minutes. Like I said in a previous post, the difference between mashing and steeping is really just time and what grains you've got in there.
So by your term of efficiency and with confirmation of steeped grains, not mashed for conversion it appears perhaps you are calculating you expected OG incorrectly assuming the steeped grains will contribute to the gravity when it really won't.
Also, you mention various volumes of wort being adjusted on the fly which will also affect your gravity readings and result in either lower or higher efficiencies results.
So to summarize it seems you need to work on your recipe creation and calculations as well as fine tuning your process to be more consistent.
This is some misleading and erroneous advice. There is absolutely no need to mash those grains, and you will absolutely get some gravity points from steeping them. The starches have already been converted by the maltster. While 30% is a little low, 50% would probably be an average expectation for a muslin bag of those grains. It is very difficult to get all the sugars out of a "ball" of grain.
So to some degree I will agree with your statement but I do not think my final reply is misleading at all or erroneous as the OP does need to refine his process to improve his efficiency. I am not really sure your assessment of 50% would be true based on steeping at 130 for 30 minutes, adjusting temps and then taking more wort then necessary from having to raise the temp (Really diluted wort) into the kettle.
This thread to me, having re-read it again, sounds as though more contribution was given to steeped grains then realistic, too much wort was collected making a diluted wort, not enough was boiled off and total efficiency suffered as a result, hence my suggestion to improve overall process. The Op's pre-boil gravity was stated as spot on and that is because all the gravity came from the recipe's DME/LME, not the grains. Once the OP then added the steeped grain wort with the extra water added he threw everything off and it wasn't accounted for. (At least this is how I am reading it, perhaps the OP might clarify in response)
I suppose we are both nitpicking or semantics are getting in the way, hard to say since some of the info is a little disjointed...........