I think the thing that pushes me over the top is your potential for appreciation and being able to add a 5th unit. If you do, my understanding is you'd be able to refi with a commercial lender, who will value the property entirely differently than a residential property (4 units or less). Which means if you manage well and collect maximum rent for the area (which, after your reno you should be able to), they'll potentially give you some equity in that valuation, which might make it so you can refi without PMI.
So if your expenses are good, rents are good, cap rate and cash on cash is good, I like it. This is a good example for understanding why the guidelines work the way they do. Your COC is awesome, for instance, because you're getting a huge loan with little down (300k for 15k ish?), but your expenses are high in part because your debt servicing numbers are huge (due to 400/mo PMI, of course, this is precisely because you're getting so much loaned with so little in). If you are confident the area will continue to grow strongly, I think it's a good buy. If it were me, I'd dump every dollar of cash flow into either extra principal payments or a construction fund to build out the 5th unit. The sooner you can ditch PMI the sooner this becomes a nice cashflow property and you don't have to count as heavily on appreciation.
I'd shoot for finding a way to finish that 5th unit in ~2 years or so, and at that point you can stop owner-occupying and be collecting rent on not only your unit, but also the 5th. That brings your monthly GOI up to nearly 5k. Of course, you'll have to figure out some way to pay for that construction, but if you're really attentive to the reno process the first time through, you can probably be the GC for that smaller reno and do it on a tighter budget. But you should be able to get a 1% property by then, and at that point you may be ready to turn it over to a PM.
Then, it'll be on to the next deal for you.