Well. Your Bicarbonate is pretty high, but you water is pretty straightforward other than that.
Bicarbonate will act as a buffer resisting the ph drop caused by the acid in your malt. Unaltered, you'll probably have better luck with beers that have high amounts of roasted or darker malts.
Even if you're just using a single pale malt, this can be fixed by adding a few grams of citric acid. If you were doing a mash with 8 gallons of water and using nothign but pale malt, I'd add about 6.5 grams of citric.
If you want to go beyond generalizations and into specifics (I would reccomend it), then you should load your values into Bru'n Water ( https://sites.google.com/site/brunwater/
) and adjust your water accordingly.
I don't think mashing longer is going to be any sort of magic bullet for your effeciency. If you're grinding your grain fine and hitting your temps, then I'd look into lowering your mash ph a bit. Your water won't need a lot of adjusting, just a bit of acid.
The guys in the chemistry forum think about this stuff all day long and they can give you more info if you want to take the blue pill and enter that whole world.