Alejandro I'm sorry to hear about the lost entries. I hate data loss, that's the quickest way to get me to find the exit.
That being said does your issues still persist on MacJournal version 7.2.1 (available on the original developers [Dan Schimpf] website)? Not that I'm wanting you to continue with something you no longer trust, I'm wondering if there's any way to get your lost entries back. If sync is the problem, I'm assuming the lost entries are still somewhere on another device. I hope so.
As for your Doc format backup, I wish apps would stop labeling that as an "export" format. It's a print format. I'm not aware of any diary app that attempts to import another diary apps exported Doc file.
By the way, if any one in future does find one that does please let me now?