I am your height. I have tried some of the "flat foot," crank forward bikes and they generally are too large and too heavy for my taste, unless you get into the expensive bikes like the Rans. But given how flat and short your rides are maybe the 24 inch wheeled Townie would work. I'd try it out anyway. Even if it is heavy and slow it will help you get stronger and faster and maybe more confident.

The other option is to work on slowly raising your seat on your Myka and see if you can get comfortable over time with the seat at a proper height. If so, you can more to a more standard hybrid with an xs or 13 inch frame. Maybe try just a half an inch a week.

EDIT: I see you did try the Townie and weren't happy. I would try the strategy of slowly moving your seat up on the Myka, which you already like. You also might try a step through design bike, that might help your confidence in mounting and dismounting. Like the step through Trek FX. Most of the major brands have them and have them in 13 inch or extra small frames. Otherwise, if you want feet flat on the ground I am only aware of the Rans having bikes that will fit us very short folks. They are nice. They cost a lot.