17. Can I connect the amplifier with balanced input to the 4.4mm headphone output port of the K7?

Yes,the 4.4mm balanced headphone out(with 4 audio pins and a ground pin) of the K7 could drive the amp well actually though it is not lineout port. You could order the suitable cable for connecting the 4.4mm port of K7 and the balanced input port of the amp.