And I believe him when he said that " it didn't occur to him " to have phoned others.
That is because you are way too biased to rationally approach any issue in this case. You even suggest that if indeed Sheila didn't kill herself then one of the parents killed her and committed suicide. Is there any evdence at all to suggest such? No but you will blame anyone than Jeremy because your irrational bias in his favor.
You admitted it makes no sense for Nevill to have called police and suggested it didn't happen until it was explained how helpful it woudl be to Jeremy if Nevill had called so then you changed your mind and decided just because it helps Jeremy that Nevill clale dpolice though there is no evidence he called and by your own admission it woudl make no sense.
You constantly ignore things that Jeremy did that make no sense just because you don't want to face his guilt. So it is totally expected you would say you believe him anyway but that doesn't mean anything in terms of whether his claims are actually objectively credible.
What you choose to believe has no bearing on the actual facts.