I had similar issues with Monte Carlo (MC) - loads of melt and really slow growth - and eventually replaced it with Marsilea Crenata - though more because I just preferred the look of the Marsilea.
My MC had started to grow and put out new runners, but it took four weeks and was painfully slow. I got the impression that it needed a lot more light at the substrate than I could give it, as I didn't want light that high due to potential algae issues at start up. It was probably a matter of patience, or lack thereof, in letting it get established.
As for the planting, the only way I found to get it to stay planted was to use much smaller portions, and use two hands. One to push the plantlet into the substrate with the tweezers, and then the other to press down gently on the plantlet whilst removing the tweezers. That we they don't seem to come back up.