You want to build a relationship built on cheating, hurting another, and basically all round lack of integrity. That will be the foundation of your relationship. Basically her 80 year old husband will be the collateral damage to you getting what you want. Calling that a solid foundation would be a stretch. You need to get your nose out of their relationship.

Do either of you have friends/family whose opinions you value? They rightfully will be wondering if you guys are off your rockers. Do you have siblings, nieces or nephews? You mentioned your "beloved" has a son. Any of them would be right to be greatly concerned for both of your behaviors/actions.

Does this woman love you? You'll never know, because what she desires most of all is security. And skipping out under cover of darkness on an 80 year old man??? No comment needed on that. It speaks for itself.

This also has the potential to end up a father/daughter relationship. It is already pointing sharply in that direction.
Once the shiny veneer of your love for each other wears off, what lies underneath that? Once you're aware of the collateral damage of her 80 year ex-husband, and she's aware of the lack of money?

You need to let her get her own affairs in order, including ending her marriage honorably. Letting her know you will be there for her once she has closed that door in her life is very different than you trying to direct it.