Hello, your project can be easily solved using phonegap/cordova, I have been working using it precisely to convert web applications made with html and javascript to mobile, this also feature some functionality for local storage in your mobile which again fits your needs.
First I'll analize your html and the javascript in it, to adapt it so it can be easily converted to mobile, then add the extras options you mentioned in the same html and functionality in the javascript, after it is working that way I'll the tools from this framework to use the device storage and store the data submited so it can be restored later. finally with other tools from this framework i can generate your mobile application for android and ios, though usually there are more restrictions to run the ios version, anyway you will be able to test the android on right away.
At least that is how i plan to solve your project with the information provided, if I missunderstood anything just let me know and we can talk on how to make this work.
Thanks in advance!