1) Does the L3+ mine coins other than LiteCoin? A generic scrypt miner?
Yes, any Scrypt based coin
2) If I have a 10mhz miner atm mining at the moment, returning about 0.0005btc per day, an L3+ at over 500Mhz should theoretically do 50 times that? 0.025btc per day? (assuming the status quo)
Mhz does not equal profit or speed of the hashrate.
Hashrate = return based upon difficulty.
Google LTC Hashrate calculator, plug in your hash rate to see what return you might see but expect that number to fall as global hashrate increases, difficulty increases.