My advice won't fix your low starting gravity issues, but re above: I'd leave it longer.azztech said:Generally speaking I wait until I have 3 days of steady SG readings before racking.
It may have reached Final Gravity, but the yeast can still clean out some off flavours if left alone for a bit. Generally I leave ales in the fermenter for 3 weeks (or 2 weeks if you really, really have no patience).
Lagers are trickier and take longer. Best to concentrate on getting ales right first.
In regards to the SG issues, It's hard to imagine a LHBS could stuff up on a recipe (but sounds like they did on that Guiness clone???). How are you measuring the volume of water you're using? For example, certain equipment I have (BMW water container/fermenter from Bunnings) has volume markers that are out by about 1.5L at the markers around 20L. If I was using that to measure out water it'd result in me using about 10% too much water (and thus lower than expected OG).