I do not think he needed to have been doing anything such as gambling or dealing in bitcoin or dodgy shares.
I think they might have under estimated how much living in France would cost,taxes are very high. I think they probably enjoyed a certain way of living and if each month they slightly over spent things could all have began to add up. At first it might have been a case of juggling payments using credit cards or delaying paying bills ,then it became harder when credit limits were reached and interest payments difficult to afford and so on until things became unmanageable. He might have been hiding the truth from her or he might have asked her to cut down on spending which she found hard to do. Perhaps he had received a bill (s) which he knew he could not pay.
I agree. Plus, he used to have a good job, with a decent salary and if he were not too thrifty, he might have been used to spending the money easily.
People plan to retire. They have a certain nest egg. But maybe, they simply can't downsize their expences. Parties for 100 people; recent marriage. It all adds up. To add to it, inflation. If he retired 10 years ago, the world, financially, was a more stable place at that time.
I think he was happy in a store because he hoped the lottery ticket would be a winning one.
I think had he won, even a little, the tragedy would have happened not that very night, but later.
One wonders if Andrew killed Dawn because he could not bear to tell her the bitter truth, that they were broke. Sometimes people overidentify themselves with heroic providers. "I know the news will kill her." (They wouldn't have, and the choice was not his to make).
Who knows. RIP and very sorry for both families.