I guess you didn't understand my explanation of how leverage increases your actual profit dollars, not necessarily the percentage but the actual dollar amount. It also reduces your risk by not having all your eggs in one basket (tenant). Think again about controlling $108,000 gross income with $290,000 vs $36,000 with $290,000. Think again about losing 33% of your gross income with 3 tenants and 1 vacancy vs 100% with 1 tenant to assess risk.
By your questions and lack of interest in how investment properties are evaluated by experts, I can tell that you are not interested in learning more so I won't continue. At least you have what you have which is a whole lot more than most people do so if you're happy, I'm happy

Although I am surprised you had no comments regarding the viability of the new duplex. It is priced too high to be suitable as an investment unless you want to use it to live in for a few years while you accumulate more cash to leverage up. The others are probably also priced too high if they were flipped. Each of the flipped properties probably has ~ $50k of profit built in for the flippers. Flipping is hard work at the beginning because you need to do a lot of work yourself and it is hard to find reliable skilled workers to help with the things you simply cannot do. At a minimum, someone needs to be checking on the job site daily to make sure that workers are showing up and following directions. The flippers you see on TV may be filmed with sledge hammers in their hands but those are staged events. In the early days the two guys from Detroit (Bargain Block) actually lived in their flips as soon as they were marginally habitable and did most of the work themselves. As they've gotten better, they've expanded their business and now are hiring out work rather than doing it themselves. They rented a building for a workshop and office and moved permanently into one of the flips. They are not laying around on their laurels relaxing though, they are beating the bushes for more properties and more worker teams to support their efforts. Last season, they did a couple of flips in New Orleans and found it to be a verrrrrrrrrry different market from Detroit.