An offline option is definitely something we will be implementing in the future, hope to see you back when we do.
Sorry, it crashed! We're working on a bug fix atm so hopefully it won't keep happening, has only happened to a couple of users so I'm not sure why... We don't have a scrub/seek option due to the fact that being interrupted in the middle of a session would effectively mean you are brought out of the state and would need to re-enter but we could consider adding it in cases of early interruptions etc.
We actually do have a one-month-free trial of the premium service, if you tap the subscribe button it will tell you about it. However, I definitely see how it can be confusing without tapping 'Subscribe', and we'll make it clearer in the new version.
Really appreciate your frank feedback, we're still-relatively-new developers and the app is quite fresh so ironing out these bugs/improvements is really important to us.