I used to work on a Cubicle Plantation where one of our managers was a motivational speaker wannabe who would try to give a pep talk when it was clear to anybody with bat brains the place was a disaster. “Let’s concentrate on all the things that are going right, not on the few things that are going not right.” We used to imitate him as the captain of the Titanic: “Yes, we hit an iceberg, not the biggest one in the ocean, but let’s stop and think about all the thousands and thousands of icebergs we didn’t hit.”
I think it’s possible. Gustavo hasn’t shown himself to be brutal, so he may merely accept Walt’s choice. More likely things will get bad enough for Walt that he’s just going to go off the deep end and fully embrace Heisenberg, and he’ll be the one that comes begging back to Gustavo.
Yeah, I thought up a cover story myself - when they met up with his ex-partners for his birthday, he could’ve claimed they worked out some sort of secret corporate espionage/reverse engineering deal, but that it was highly illegal and would’ve sunk the company if anyone found out, so he had to be very secretive, coming to the lab at all hours, telling no one, etc. If he would’ve given this excuse to his wife, it would’ve also kept her from prying about details about how they’re paying for his care.