Lance's deal is almost definitely covered by insurance. As was Verlander's. If a guy is in the first 3 years of a deal it is very likely, from everything I've ever seen and heard that, it has an insurance policy. Maybe not to cover the whole amount, but likely with McCullers being young it does. So the time he's on the DL they are likely getting insurance payments.
Insurance payments don't count against the cap either, so unless it's hugely prohibitive they have them. It's part of the reason that the Giants and Mets wanted to renegotiate with Correa. They couldn't get insurance at rates that made sense unless they took money from his contract to do it.
The Astros have made money hand over fist. Abreu and McCullers deals will not effect winning in any shape or form based on money. They will hurt because they are two previously good players that aren't contributing. The Astros could easily afford to pay into the top tier of the luxury tax, and I think they've been managing money accordingly the last few years because on the outer end of the window they know they will have to. Crane is not going to allow this team to not be playoff competitive unless he has absolutely no choice