You could try rotating the stem 180 degrees so that it extends towards the seat. This should make the top tube length a little shorter if that is a problem. I think I have 150mm or 145 mm cranks on my daughters mini. The gearing sounds OK for a start. The brake lever is a tough one. I am using a vintage DIA-COMP one that came with MX 1000’s. It has the adjustment screw for little fingers. Hope this helps.