Your FG should certainly be in the 1.005 - 1.010, but your OG seems low too. You didn't say how long you ferment your batches, so that could be one problem. Let them go for a good two weeks before bottling. I'm curious to know if you can detect an appreciable sweetness to the final beer? If so, you're just leaving unfermented sugars by not fermenting long enough. If not, you may not have started with enough sugars. When you pitch your yeast, what temp is the wort? And do you see vigorous bubbling and foaming action after 1-2 days of pitching the yeast?
When I started, I tended to brew batches with lower than expected ABV, but more like 4.5%-6% rather than 6%-8%. I've added extra grains (oats) and let the fermentation go longer - both to good effect. Your OG is a bit low, so you could consider adding more malt extract or other form of sugar.
In the end:
1) make sure your yeast is vigorous. You may want to consider starting your yeast in a warm solution of water and extract or even sugar.
2) Make sure you OG is up to spec. Add more extract if necessary.
3) Let the batch ferment for at least two weeks at about 72deg or whatever temp your yeast instructions recommend. Avoid the heating pad. The cooler your environment, the longer your brew will need to ferment. I've lagered beers for over a month after an initial 10 days at warmer temps.
4) Use a sanitized thief to pull out a sample to test for FG and if still to high, let it ferment a few more days.