If you're able to conduct your interview virtually, you could post on reddit or hacker news. Other ways include attending developer events and asking the developers in person. Depending on your area, you should be able to find developer events on meetup.com.

Event marketing is pretty low hanging fruit. Create an event or meetup to target your small business customers. The event should be a based on a topic of interest to your customers. ie. A panel talk by local entrepreneurs giving growth tips. Also include a small networking reception as part of your event. As host of the event, you have the advantage of telling the audience more about your company and services during the introduction. You can make the events monthly or quarterly to ensure that you are constantly engaging with your customers.

The solution for your team largely depends on your team and tools that you are currently using. If your team is already using github, then github issues might be the simplest tool to use in your work flow. There are other bug tracking software that can plug directly into github issues.

It depends on the type of startup and current stage of your startup. I would advise to start with tools like Appcelerator and PhoneGap and deploy on both platforms for validation. (I'm assuming you've already done some level of customer development and validation before thinking of building a mobile prototype) Depending on your app, and what your learn from the use of the app by your customers, you may find it necessary to eventually invest in a native app.