I'm vaguely aware of the challenges that text expander and similar application run into when attempting to get them to work on iPhone exactly like they work on laptops and desktops. However, one potential work around would be to work within the TextBlaze dashboard application on mobile Safari.
I use this approach regularly for long static boiler plate text by simply searching for the shortcut in the TextBlaze dashboard and then copy/paste into the application I'm using. Sure, not as nifty as a shortcut in the application but way easier than typing and more organized than keeping all my phrases in a doc file or sticky note to copy/paste from there.
What might be an option for dynamic forms would be resolving the resulting prose in the TextBlaze dashboard window (or pop a new tab) and providing the user the option to copy to clipboard. I get it, not perfect, but for those of use that mostly utilize the dynamic form feature, the ability to assemble dynamic paragraphs quickly on an iPhone or iPad is easily worth the manual copy/paste step that may be required.
I've mocked up a rough Angular example so it is possible although a slightly different work flow. It is way better than trying to type long entries with a screen keyboard.