Is it actually tinfoil? Or a proper reflector? I'm asking because tinfoil is one of the worst reflectors you can use. I know it looks like it's reflecting the light, but tests have shown it doesn't do a good job. A white painted background will do a better job.
On another note, I've read that anything over about 10 hours isn't used by plants, so increasing your light time won't make the difference. That said, I know a lot of other people here leave their lights on for 12 or more hours, but I notice that even in my lower light tank, the plants start to close up for the night after about ten hours. Anything over that just benefits the algae.
As other people have already said, 2wpg should be good for dwarf sag. I have it in my 29g and it did well even under my old lighting, which was only about 1.5wpg.
Edited to say that Wasserpest is a faster typist!
29g Eheim Classic 2213, community, heavily planted, 65W CF, 2x Hagen CO2
20g Fluval 3 Plus, nothin' but shrimp & snails, 65W CF, Hagen CO2