Hi there,
The requirements look quite clear and straightforward to implement. I'm not exactly sure what you mean with leaving only 1 link while posting to blogger. I suppose you want to remove the extra links and leave only one but it's not clear which links are supposed to be removed and which should be left while posting to blogger. That'd likely make sense if I can take a look at a couple of your posts.
Anyway, I'll create this as a plugin which you can install from wp admin dashboard, just like any other plugin. Still, I'll provide instructions and help if needed. It'll be ready in 24h, thanks.