Well, some of this is normal - you are a teenage girl with strong sexual desires triggered by your normal hormonal development. It is also very easy to fall for someone online, especially when you feel a great empathy toward them.

Fantasies and cyber relationships can be great fun and a real turn-on.

Dom/sub games can be a fulfilling part of a full sexual relationship.

However, you need to distinguish between play/fantasy and reality here.

The 'wrong' part of this situation is your online playmate.

This guy is probably rather less 'nice' (whatever that means) in real life than you imagine him to be online. Nice 34 year old men usually have fulfilling lives with mature female partners. They do not trawl chatrooms looking for inexperienced virgins half their age.
Age difference in years is not important, but you have a yawning maturity gap here - you need to live some and get experience of real relationships before you will have enough judgement to make an informed choice about committing to a live-in relationship of any sort, never mind the sort of SM fantasy world he suggests. He lives with his grandparents for God's sake! Does he plan to get his own place or are Grandma and Pops into his SM fantasy too??

You write a lot about the sexual aspect of your relationship, but I wonder how well you really know him as a person. Have you had much non-sexual conversation with him?
Have you considered some of these questions:

• What is his relationship history? Has he been married or in a live-in relationship before? How and why did it end? Does he have children? Does he pay child support?
• He does not own or rent his own home. This is very unusual for a man in his thirties. Does he have financial problems?
• What is his job? Does he have a realistic chance of getting his own place soon?
• How does he spend his time? Does he drink much? Or use drugs?

You may think this does not affect you, but if you move in together, you will quickly find that his problems become your problems.

You acknowledge that this could end badly, but I wonder if you appreciate just how badly. Maybe you think that you can just pack your bag and go back home if it all goes wrong, but it may be less straightforward. Young women who get drawn into abusive relationships lose confidence in themselves and have their self-esteem undermined to the point that they find it near impossible to leave. They may also be manipulated into taking on debt to the point where their independence is severely compromised.

You may think you are not a victim. This could never happen to you. But it can. My daughter was a popular, confident 18 year old with lots of friends when she moved in with an abusive man. Within a year she was a shell of her former self. He got her into drug use, physically abused her, emotionally blackmailed her into having an abortion against her normal judgement - and much else she has only hinted at. She even attempted suicide and needed in-patient treatment to repair the psychological damage he caused her. She eventually managed to leave but carries the emotional scars to this day.

Frankly, if you need to seek advice about this from an online forum, you are nowhere near mature enough to be contemplating this move.
Give yourself a break. Meet some real guys nearer your age and date them. Online fun is fine, but don't confuse it with real life.