Since you're clipping at guitar level, try line level next time.
Btw, it's a line level output on the G7, so set the Tascam to line level, -10 dBm settings. Experiment with either ASIO or WDM drivers and see where you can get lower latency figures. For example, my Emu 1820 bottoms out at 10 ms when using WDM pero kapag ASIO gamit ko, I can achieve latencies as low as 2 ms. It all depends on the card's drivers.