Hi! If your .txt actually has 70k unique lines, it definitely sounds a bit suspicious that it exits so early. Skipping examples is expected (and kind of the point of using textcat.teach), but it should only happen once you've moved through all the batches. When you see "no tasks available" and reload the browser, do you get new examples? This could indicate that something on the server is taking too long and the queue runs out before it gets new examples 
Otherwise, what you describe here sounds similar to the question in this thread so I'd probably also give similar advice:
If you have a lot of patterns, I think it'd probably be a good idea in your case to start with some basic pattern matching with prodigy match, collect some initial data to give the model a head-start and get a feeling for how common/rare the individual labels are.