There really are no hard and fast rules with nicknames plus honorifics when actually speaking. Usually something will end up sticking even though it may be "wrong". For someone new to Japanese, go with -san (for older or business) and -chan (for younger or girlfriends) and then follow the lead of the Japanese people you are with.
For example, one friend of mine is よちゃん. This is what everyone calls him, including younger people and people the same age, he even introduces himself this way in friendly groups. This would be wrong according to the rules, but is what the native Japanese call him.
I've been called ロスちゃん among friends as well as ロスピン, though the ピン is reserved for girlfriend and boyfriend in my experience. In more formal situations, I am generally called ロスさん, even though my last name would be more "correct". When I am the customer, though, it is always last name + さま.
So, really just follow the lead of those around you, this is an area where the rules often give way to whatever feels right.