Instead of disabling velocity on the piano, check the user manual and see if there's a way to scale it. Pianos by nature need the full velocity range, but most sampled instruments don't, so excessive velocity range is often a nuisance. If the Casio doesn't offer velocity scaling, most Kontakt instruments do, so you can always adjust the velocity range after the fact.
Getting adequate volume from Kontakt is sometimes a problem if the instrument's CC7 range is too low by default. You can edit the Kontakt instrument to raise it - go into the instrument options and there are selections for the CC7 range. I often have to bring it up to 0db or even higher to get suitable volume while recording.
19ms of latency will make playing soft synths in real time awkward, especially instruments with fast attacks. You'll need to get down to half that or even less if you want to use, say, a marimba or other percussive sound. Reducing latency is largely a matter of decreasing your sound card's buffer size, but can also be accomplished with higher sample rates. Just going from 44.1KHz to 48KHz (which is the native rate for the RealTek) will knock a couple milliseconds off.
The way I deal with soft synth latency is to monitor the hardware synthesizer while recording MIDI and then re-routing the finished MIDI track to a soft synth. Because you're using a piano rather than a general-purpose rompler, this will probably only work for percussive-type sounds. If, for example, you want a harpsichord, play it as a piano part while monitoring the Casio directly and recording the performance as MIDI. Then find a harpsichord instrument and route the MIDI track to it.