When a brewer is creating a beer such as RIS, Wee Heavy, Scottish ale, doppelbock or for that matter any style of beer. He really has to know about enzymatic action and how it works. To create beer, mash thickness, pH and temperature are controlled. The brewmaster knows that enzymes thermally denature with time and temperature, so he has to adjust the process to slow down the denaturing part. A thick mash preserves enzymes, enzymatic action changes in a thick mash. Another thing happens, mash gelatinizes at 149F when pH is below 5.5. When mash jells, enzymes change gears, conversion slows down. When mash jells, it is caused by amylopectin. But, now, we have a problem Houston. Temperatures at 156F denatures beta real quick, even in a thick mash. So, action from beta is limited, formation of fermentable sugar and B-Limit dextrin are limited. The longer beta is active, the stronger the beer becomes. After beta denatures, alpha is left and alpha produces non-fermentable sugar and A-Limit dextrin. Limit dextrin and protein are what creates mouthfeel and body.
If a brewmaster produces world class beer and puts food on his table by selling that world class beer. I will gaurantee that he will never tell anyone how he produces the beer. When some random guy walks into his brewery and says. Hey, Mr. Brewmaster, how about telling me your recipe, your water chemistry and the process you use to make your beer. Because after I leave your brewery, I'm getting on the computer or Im going to write a book and broadcast your secret all over the place. Do you think for one minute he is going to tell the guy how he does it? If you believe that he will, there's beach front property on the Planet Zyclor that is being given away, that you might be interested in. Charlie Papasian believed it. There's a lot more to it. But that's it in a nutshell.
Hot water doesn't liquify starch, alpha amalase does. Starch will begin to burst at 168F. When it bursts, amylopectin is rapidly released. That's where trouble begins when a brewer that uses the English method uses a mash out procedure. Mash out came from the tri-decoction method. In the method mash is boiled, hard starch bursts. When the mash boils it jells up. The boiling, jelled decoction is added back into the main mash to reach beta temperature. Beta will reduce the amylopectin. The 2nd decoction is boiled and the same thing occurs, amylopectin is released. The decoction is added back into the main mash to reach alpha temps. When beta and alpha cannot reduce the amylopectin any farther than Mother Nature allows, A and B-Limit dextrin is left. That's part of the reason why the tri-decoction and Schmitz methods produce higher yields and higher efficiency than any other brewing method.
When the OP brewed the brown beer at 1qt/lb, he failed to mention conversion time and conversion temperature. No mention was made about the method that was used to determine if conversion took place. The mash might not have converted during the time period. The brewer applied the rules that he read about and that works in one process, to another process that uses a different rule book.
Marris Otter is the only British malt available to a homebrewer that has low diastatic power. The malt converts easily, modification and protein level are standard. British malt is easy to work with. Try using under-modified, low protein malt.