Your now doing a 180 going from logic to emotion.
Jeremy never told Julie anything. His alleged confessions to her not only contradicted the crime scene evidence, they contained false information she could only have got from the relatives or tabloids. Her testimony is a complete parody.
You cannot gain a reliable insight into someone's physiognomy by Just reading a few letters. Plus you have only seen snippets of his letters to Colin and none of Colins messages back to him.
You are not being objective Steve
Jeremy speculated to the only intelligent woman in the vicinity who would listen to him, and we get a good outline of how the crime developed from the initial idea of poison to the shooting which ultimately ensued. You were never going to get an exact account from someone whom Michael Deckers described as a "
Walter Mitty character" but there was enough of substance for Stan Jones to realize its import. The hitman story coming at a time when Julie was in the last chance saloon and desperate to be believed by the authorities is testament to her and her story's veracity, shocking as its relation was.
As for Colin he initially felt an affinity with him as Jeremy played on the outsiders leitmotif, with Colin possibly forced into marriage due to Sheila's pregnancy and Nevill and June finally putting pressure on their son to make an honest woman of Julie, which Jeremy had no intention of doing. He used her as he used others on the Farm, who were informed of their inferior status in no uncertain terms. When Jeremy saw his inheritance diminishing by Sheila's hospital fees, the figures lying on Nevill's desk along with other paraphernalia upon which an increasingly lugubrious father reminisced, the possibility of a private school education for the twins and of course Sheila's share in her own right Jeremy seized a once in a lifetime opportunity which presented itself that August week thirty-one years ago when all were gathered under one roof, those five sitting ducks unable to extricate themselves from Jeremy's act of diablerie, that necessary act for him to start life anew.