I am almost convinced the wife (and possibly daughter) off'ed the dude and his mom and concocted a story about money owed. The suicide letter is so clinical, it pretty much only lists the monies owed, no last word for wife or daughter.
Also, why did his mother need to die?

Let's assume you are a middle age man, heavily indebted, creditors chasing you. You commit suicide.
Is there ANY REASON you will also have your mother (probably 70+) commit suicide with you? Makes no goddamn sense.

Keep in mind the requirements for Abetment of suicide under IPC 306 is very stringent. You have to actively coerce, aid or abet in the process or at least ask in some form to do so. Simply owing money (unproven) or even suicide note does not pass the threshold.