This deal is mainly operated as a business so I think that makes the most sense.

What further analysis should I be honing in on and key factors/metrics/info that may be providing inaccurate numbers?

One thing to add is that when you buy a new build, your PITI will likely not be factoring in the correct state tax number.

What are your main investment goals—cash flow, appreciation, or something else?

Hopefully this helps clear up the main point of your post!

If I put myself in the shoes of the outside partner/investor friend, I would be very concerned because: 1) unclear and/or potentially conflicting business plan, 2) even with clarity in the BRRRR business plan, unclear in the viability of pulling it off with these market conditions, 3) the chances of dispute seems very high, especially if you're going to live in. 4 years ago, I went through a  similar thought process when purchasing an investing property with mainly my family money, while considering an outside investor to rehab for higher STR ROI... 

But it’s clear you’re a smart investor who knows the long-term benefits real estate can bring.I keep reminding myself why I stick with real estate: you can make money every month in four different ways:Cash Flow – Passive income to live on.Appreciation – Long-term property value growth.Depreciation – Tax benefits that reduce your taxable income.Tenants Paying Down the Mortgage – Even if you’re paid off now, this is one of the biggest wealth-building tools for leveraged properties.It sounds like your main struggle is the stress of active management—and trust me, you’re not alone.

I mainly wanted to know if other investors in syndications were experiencing the same thing.  

Experienced managers can help evaluate potential investments by providing insights on rental demand, market rents, tenant preferences, and location-specific factors that affect leasing success.For example, rental properties need to be close to conveniences like major roads, shopping, and schools.

Price is often not the main or the only concern for the seller, they have other needs.