help creating pdf form

I am working on creating a PDF and need to see if I have the ability to complete the following. I am using Adobe Acrobat Pro DC and PDF Expert on the Ipad to complete the form.

I have created a list box, which upon selection, exports the selections "export value" into a text box.

     a. is there a way to have the text box shrink and expand depending on the numbers of items selected in the text box. (For example, I have 10 items in the list box, so      I have the text box to accommodate all 10 items, but if the user only selects 2 items, I would like to shrink the box, so that there isn't a lot of white space between      sections and have it create a new page if it needs to)

     b. Is there a way to make this text editable? (For example, one item in the list is for "demo" but sometimes we are demo'ing drywall, sometimes baseboards,      sometimes flooring, so I didn't enter anything in the "export value" field of the option "Demo", but when I try and edit this field in the document, it lets me type, but      when I click out of the text box, it disappears. 

     c. Is there a way to make a text box "disappear" if nothing is typed into this field?

Any help would be much appreciated. Thank you!