(1) If you choose to use the REST API, you would have to grab a user’s timeline and then do pattern-matching for the hashtag in your own code, as the REST API does not currently support a search parameter for the [node:9537, title=“GET statuses/user_timeline endpoint”].
However, with the Streaming API, you can use the [node:10392, title=“GET user endpoint”] with the [node:5892, hash=“track”, title=“track parameter”] to stream only Tweets that include the given terms (including hashtags) from a given user’s timeline. Because you said that you need this to be as close to real time as possible, I suspect that this would be the best option for you. (Keep in mind, however, that if you find yourself needing to backfill data, you will have to use the REST API and do the pattern matching in your code anyway.)
(2) I’m not sure that I understand your question, but if I didn’t implicitly answer it above, I might suggest taking a look at our list of [node:126]. While we don’t support them directly (and we don’t necessarily endorse any one over the others), many of them have good resources and documentation to help you in developing your app.