Does hook_node_info() have to be in .module or can it be in .install? due to some code sharing it would help me quite a bit if I could put hook_node_info() to a .install file instead of a .module file. Now, from what I've tested it doesn't seem that it could be a problem but then every tutorial says you have to put it in .module file.

And the official documentation is silent in regards to this problem. So my question is, can I do it without braking something?
hook_node_info should be in the .module file. However, you could implement the hook in the module file and then just call module_load_install from there to include another function in the .install file, if that helps. Another option is to export the content type using a module such as Features instead.