Is there a better way to wire this?
Not sure if it's code in your area since this is a building code issue but new hard wired smokes must be interconnected. I'd venture to say it is code in most places.

This means you have to feed the smokes at any one, then run 3-wire between them. Typically the red wire is used as the interconnect wire. Some areas have requirements that say the smokes must be on a dedicated circuit, some say they must be on a local lighting circuit. The local requirements on this vary.

I hope you do not mean you are using only 14/3, but a mix of 14/2 and 14/3. 

Also, I would NOT put the whole house fan on this general use circuit. No valid reason other than convention and to lessen the load on such a circuit. 

Also, I'm not sure what you mean by line and load in your diagram. That makes no sense as far as the diagram goes.