And wasn't a religion problem throw into the mix too ? Elvire is a Catholic and her family did not want her to become a Lutheran ?
Yes, that certainly would have been a barrier but since they had already decided to marry in contravention of the House laws (and the resulting consequences for Gus in losing his inheritance), this would not have been a deal breaker. If it were the only thing standing between Gus and his inheritance, it's something that can be remedied if the appetite is there to do so. The not-noble in four generations can't be remedied.
Bottom line is that Gus was willing to forgo his inheritance for Elvire. What happened after that - why they split - is speculation but I think we had two sets of strong-willed parents and two essentially less strong young people.
IMO, it's just about the strongest statement of love that a man in Gus' position could have made, that he could/would give up his family inheritance for love - and still look like he's walking on air. Whatever happened after that must have been nothing short of a (metaphorical) earthquake.