Recently found someone using a very similar logo as mine

I recently found a company using a logo very similar to my distinctive logo. I sent a generic cease and desist letter and the guy called me and said it was unlikely I could win if it went to court. My company is Social Magnets and has a large online presence. His is newer and has little presence. My logo is two magnets linked together to form an M so is his. I have a few questions. I was pretty sure from checking nobody else was using this design of a logo when I made it. I have been around for about 4 years using it online and his website is about a year old. He wanted me to give him permission, but my concern is If I haven't registered it as a service mark, what protections do I have if I have been using it first/longer.

Can someone else in response to my notice go trademark it and I would have to stop using it? My concern is as I build my brand I don't want other people coming after me in some weird way. Also is there any protection before or without a registered service mark? and any protection in the process and if not how long does it take? Lastly, their name is Magnet Social SM, mine is Social Magnets. Is there a way to protect the use of social and magnets in regards to marketing and consulting like Apple is to Computers and if so is this expensive or beyond a regular service mark. Thank you.