Hello Francisco,
Thanks for your post - but I have feeling that URL you've provided is same I already saw several times, which refers in fact to some MS docs; thing is that it is not much relevant, as refers to config where both, AX and PS are on same box; because of MSMQ, certificates, accesses, differences between private/public MSMQs it is not much relevant.
Also regarding what you wrote:
"Project Server" must have "Synchronization Proxy"
"AX2012 Server" must have "Synchronization Service"
To be clear, according to MS docs proxy needs to be on PS indeed, however sync service may be located on any server (PS / AX), thing is that it may be running on only one at same time. This is just to not to push someone who may read our conversation in the future into unnecessary reinstallations :)
regards
Tomasz