Really depends how many hours a week you spend on customer support. If it's enough (20+ hours/week) then a part-time dedicated customer support rep makes sense. Also depends on the kind of queries you receive. In a previous very tech-heavy startup 95% of customer service had to be run through the dev team as the queries were way too techy for the sales guys.
We started using GrooveHQ about two months ago. So far really great as it's affordable, fast and simple. Before that we tried HelpScout, Zendesk, Freshdesk and another one and all of them seemed more complicated as they're more complex.
Check out glassdoor as they have thousands of companies listed with reviews by current and ex employees. Take the reviews with a pinch of salt as you can imagine that someone who got fired might not be in the best mindset to leave a review ;)
I've had the secure problem in a previous app. Had to change the subdomain of the user, luckily he was inactive.