Adding extra wort to fermenter to improve watery beer?

I am working on a simple ESB with the following recipe:

7lbs pale malt
1lbs muntons medium malt dme
1lbs briess dme golden light
5 oz Demerara sugar

hops:
60 min 1.25 oz northern brewer
30 min 0.5 east kent goldings
5 min 0.5 east kent goldings
40.5 IBU

o.g. 1.049
Nottingham dry ale yeast


During mashing I had problems reaching the right temperature, probably because I failed to take in to account the low temp of the malt before mashing and temperature of the room , and I ended up having to add way more hot water than planned. In the end I reached 150F, but with a very thin mash.

Went along anyway, and it has been fermenting for two weeks. I took a sample today; gravity is ridiculously low at 1.007, color is too light and taste is watery.

Would it be an idea to add some more wort at this point to try and get some more flavor? I still have a 1 lbs package of munton's medium malt dme, so I was thinking of making some strong wort with that and add it? I still have enough space in my fermenter to add half a gallon or so.
Also still have some 100l crystal I could use.

Good idea, bad idea?

I wouldn't fool with it. The 3 problems are that you didn't use any crystal malt, you added sugar, and that you used Notty yeast--it dries the heck out of beer unless you mash very high.

I recently did a pale ale with notty and a good bit of crystal, mashed at 157F and it still went from 1.060 down to 1.013.

Just let it ride and you'll have an easy drinking session beer. Adjust the next batch accordingly.