slider on small screens

I am building a web site in “Spacious”. See https://next.davelevy.info

On my two phones, Samsung 4 & 5 and iphone 6+, I find the slider is rendered seemingly proportional to the picture. The text objects are not. This means on small screens, the comment box and hyperlink button are not visible and the slider image is too small compared with the widget objects that follow. (This only occurs when the phone is in portrait mode.)

I have not dived into the code to see if I can fix this, or offer a solution but am considering using wptouch as a workround.