Peter's reaction to the big announcement about the promotion and the engagement seems to make that pretty clear. (Unless he had a real poker face about those things!)
Speaking of scenes that would've been interesting, I always think it would've been nice to see Beth's mother really noticing Peter's reaction to those announcements, and changing her mind about him, or at least having some doubts about the whole "fortune hunter" thing.
It would even have been nice to see the two of them "commiserating" about Beth's behavior, since by now they were BOTH put off by it.

Bryce was the brother she killed. It was Peter that loved her.

I think he did love her. He was a very moral man, which is shown by he's not bothered about losing a job. We don't see contents of the letter written to Peter, so if we assume the Chadwicks hold a lot of sway in the industry, Bryce could have made it hard for him to get a job elsewhere. (As in Bye Bye Sky High... when the male secretary is told he won't get a job anywhere else)

He also dislikes her complete transformation, not just in her fashion style but her whole personality. And the fact that she suddenly is making decisions for both of them - like announcing their engagement when he hadn't even asked her to marry him.

Finally, his morality is shown by the fact that despite he swears a statment that he heard the shot and then the alarm.

To be clear, the coroner's inquest was not a trial of Beth Chadwick. It was strictly a determination of how Bryce Chadwick came to his death. The jury ruled his death an accident. But if further evidence emerges to establish that he was in fact murdered, then the murderer should certainly be put on trial. The fact that the coroner's jury reached the wrong conclusion about the cause of death (based on incomplete information presented to them at the time) shouldn't mean that a murderer gets a free pass.