I agree, selling arms from the 32nd floor of a tourist resort would seem rather silly. It's just as likely he made his riches through drug trade. We know he profited from the sale of real estate so he had a source of funds and he appeared to live a relatively mundane lifestyle albeit most of it in casinos where many of his needs were complimentary.
I'm interestered in hearing more about his relationship with MD. IMO she knows much more about him than was released by the media, "a kind, caring, quiet man". SP was married twice but the marriages were relatively short, 2 and 4 years iirc. No information of other relationships. SP met MD prior to 2013, when he visited her family in the Philippines. MD may have spent more years with SP and have been closer to him than anyone. Had this relationship broken up? Don't know although MD told the media she thought it had when she was sent the $100,000. I don't think her vague explanation is fully credible.
From CNN
"Danley, 62, who travels on an Australian passport, arrived in the Philippines from Tokyo on September 15, then left for Hong Kong on September 22 and flew back to the Philippines on September 25, said Maria Antoinette Mangrobang, a spokeswoman for the Philippine Bureau of Immigration."
http://www.cnn.com/2017/10/04/us/marilou-danley-vegas-shooting-paddock/index.html
One of the things that caught my eye was Sept 22nd - Sept 25 just happened to coincide with the downtown Life is Beautiful concert in LV. SP reserved a room at the Ogden during that time. On the 25th he checked into Mandalay Bay. Perhaps the dates of MD's travel are a coincidence but I couldn't help but notice how they overlaid.
Why did she fly to Hong Kong and who did she see? Could jealously, and broken relationship set SP off the rails? Yes I expect this is probably a boring theory but I do wonder.....
edit to fix quote