It's a 10g, wpg doesn't really apply but dang that's a lot! That being said, I've got 2X23w CFL's on my 10g and I barely dose ferts (root tabs mostly) and have been very lazy with my Excel. Things are fine except for gsa on my wood. But I also have an interrupted photoperiod (7a-10a, 6p-10p)... I'd say with diy co2 you'd be okay, as long as you're maintaining a good fert schedule and use an interrupted photoperiod. The trouble with diy co2, is keeping a steady bubble. bsmith does make a good point about pressurized... it's a leap, but really can be worthwhile.
re: the c. wendtii, I saw a claim that it reached the top of someone's 125g tank - but honestly that's a bit of a stretch. My c. becketti is about 6" now... and I believe wendtii is considered a larger crypt. It's also wide - which is something to consider.
Dwarf Hairgrass supposedly grows around 3-4"... I'm getting some soon, and I'm hoping it stays closer to 3 than 4.