Update: I test rode a Cannondale Synapse Carbon 5 and 6, Trek Domane 4.5 and Cinelli Saetta Radical. The Trek felt like I was riding a really comfortable recliner sofa, the Cannondale felt comfortable but also quite zippy and the Cinelli was just too aggressive.
I'm not surprised you've not got an answer. I've ridden a synapse. I didn't like it but that doesn't mean you wouldn't, or shouldn't buy one.
Whether or not it will solve your fit issues... is another thing. It sounds like you might benefit from a bike fit.