Low OG - Adding more DME/LME

I bought a Scotch Ale DME+LME kit from my local store and according to the recipe I should have O.G. between 1.045 and 1.050 but I ended up with about 1.036 at best. My specific question is not whether to add more extract. Instead, I would like your opinions on using a gallon or so of the original wort, which has been fermenting for three days now, to boil the additional extract so that I still end up with five gallons. Thanks!

If you boil beer, it will be ruined. Maybe consider 2 lbs straight LME from a sealed container.

Maybe pasteurize enough LME to make your target OG, let cool while covered and pitch at ferm temps. I think 170 degrees for about 10 min should do it.

This may sound stupid, but some of the kits that state those high abv percentages state that it will make less pints than other kits. In all fairness, you could just reduce the water in any beer kit and make a higher abv beer - the difference being that the brewery that made those kits have probably got the recipe right for that strength.

Next time you could reduce the water. Do not ruin you batch by trying to modify this one this far down the line.

It is almost impossible to miss your OG if you used all extract. Usually OG measurements that differ from kit recommendations are a result of poor mixing of wort and top off water. Unless you did a full boil and have 100% confidence that your OG measurement is really lower than the kit recommendation, I would advise you to do nothing.

i had the same problem recently, for me it was a mixing problem. Especially if you have warm wort and cold water, they dont want to mix... let it ride. Mine came out fine..