Hi Bob! I am inclined to think that Cavallero actually committed suicide. First of all, the theory of a homicide may have been put forward for two reasons, i.e. for the afroementioned religious one and to replace his widespread image as a pro-German and pro-Fascist military leader. The only evidence that could have been in favour of his homicide is the note in Marshal Caviglia's diary about Cavallero hugging him shortly before being taken away by the Germans and whispering in his ear: "They are going to kill me". But we should note that the published version of Caviglia's diary is full of interpolations, therefore whoever modified it may have changed also this episode. Moreover, maybe Cavallero was really fearing for his life when he met Caviglia, but what happened next does not seem to justify this fear. After all, Marshal Kesselring was in good relations with Cavallero and apparently he asked him to command the new Italian fascist armed forces.
Why might Cavallero have feared for his life? In the late summer-autumn of 1942 Mussolini was seriously ill, and Cavallero had planned a regime change in case of inhability of the Duce or of his death, but it was still within the limits of the Statute and would have been carried out only with the King's consent: hardly a crime that would have caused his death about a year later, after weeks spent in jail upon Badoglio's order (twice: he ordered Cavallero's arrest shortly after Mussolini's fall, the King ordered his release, but then Badoglio had him arrested again in connexion to the alleged coup planned by Ettore Muti, who wasn't plotting anything against Badoglio, but was looking for a way to open contacts with the USA for an armistice).
The only physical "evidence" about Cavallero's death is the fact that he had shot himself with his right hand, while he was left-handed. But the Beretta 34 is made to be used by the right hand and, anyway, militars were instructed to use this hand even if they were left-handed. As you may notice, Cavallero always kept his pistol on the right side, as is required by the uniform.
Finally, Cavallero's autopsy was carried out by gen. Alfredo Bucciante, commander of the Medical service of the Army, and his son, the journalist Giuseppe, was present at this operation. Giuseppe Bucciante wrote in the 1984 edition of Cavallero's diary, which he had edited, that neither his father nor him had noticed any evidence to suspect that the Marshal had been killed. In my opinion, this testimony closes the case.