You’re cutting right through Kane’s ego to the heart of his tragedy.
You're right: his "doom" wasn't a lack of money or opportunity, but his refusal to de-center himself.
To live a better life, Kane would have had to trade his need for power for the vulnerability of connection:
The "Workaholic" Trap
You hit on a crucial point about his hours at the Inquirer. Kane used the paper as a surrogate for real intimacy. By working 16 hours a day, he could maintain the illusion of being needed by millions of strangers, which felt safer than being truly known by one person at home.
The Lesson of "Rosebud"
The sled represents a moment where he was loved for who he was, not what he owned. To have a "better life," he needed to realize that the "loving family" he lost couldn't be replaced by statues and opera houses.
Correction vs. Madness
As you noted, he "went mad" because his only tool for solving problems was money. When Susan was unhappy, he built her a castle. When the public didn't vote for him, he bought more papers. If he had the self-awareness to stop "fixing" things with checks and start listening, he wouldn't have ended up in that hollow palace.
Breaking the Cycle
Plenty of people raised in cold environments, like real-life figures the film was based on, go on to find happiness. The difference is they learn to trust others. Kane's tragedy is that he treated people like subscriptions—he thought as long as he kept "providing" the service, they weren't allowed to cancel.
As Jed Leland tried to tell him, you can't just "love 'the people' on your own terms." A better life for Kane would have started with the word "No"—as in, saying no to his own impulses and allowing others to have their own voices

He could have attended a psychiatrist to begin with; he would told him that he suffered an oedipal complex. Just that knowledge would have helped him greatly.

Honestly, he should never have gotten married. That's probably it in a nutshell- his work/home life balance would've been fine, his political aspirations would've been far less messy, & his friends more respectful of him.
Probably could've travelled a lot more & worked a lot harder. Instead, he kept getting married as if collecting things to make him happy, when things & people he collected (or anyone of us do) offer no such reward.
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His first wife told him what he needed to do/not do. He spent a whole lot of time with his newspaper business. He had a very large very capable staff to handle things. Nothing would have changed if he spent only 12 hours a day there instead of 16. He might have even been able to spend less than 10 hours a day there.
But, he wanted fame even more than fortune. Cutting back on his hours with the paper wouldn't have impacted his fortune in the slightest. It would however impact his fame a great deal.

He was too much of a control freak, and he figuratively pushed everyone away. Kane needed to see this in himself and try to make corrections and adjustments. He seemed to go mad toward the end.
"I will not go down in history as the greatest mass-murderer since Adolf Hitler!" - Merkin Muffley