Not a CPA, but I will weigh in. Hopefully, one of the CPAs in this forum improves on my response if I have misinformed you.
1. Your depreciation basis on the dwelling structure is calculated on what you paid for the property, then you add your renovation cost to the depreciation basis you had calculated. In your scenario, you paid $101K for the property. Use the tax assessor 65.5% ratio to arrive a an initial depreciation basis for the dwelling structure of $65,975. Now add your renovation costs to arrive at your final depreciation basis of $106,475. Land is not depreciated. Depreciation does not start until you place the property in service.
2. Residential rental property only has three asset classes -- 27.5 year property, 15 year proprety, and 5 year property. For a 1-4 unit property, a formal cost segregation study is generally not worth the cost for the tax benefit derived. Since you did a major rehab, everything you did inside he property is in the 27.5 year asset class, so it would be depreciated with the building stucture anyway. If you purchased new free standing appliances the cost of those appliances can be depreciated separately from the dwelling structure over 5 years, and their cost would not be included in the renovation cost you added to the dwelling structure depreciation basis as you outlined,
3. For your BRRRR, only include the initial financing closing costs in your cost basis. When you refinance, the closing costs are amortized over the life of the loan, not depreciated.
4. This queston is a bit vague. You used financing to purchase the proprty, so your refinance will pay off the first loan. Interest on the portion of the loan that paid off your first loan is deductible interest for the BRRR property. If you are doing a cash out refinance, then interest on the portion of the refinance that exceeds your original loan amount can be deducted as an interest expense on the Schedule E for the investment property you purchased with that money -- not on the original BRRR proprety
5. I believe so, but will defer to someone with more expertise in this area.
6. HELOC. Yes, but the interest is expensed on the Schedule E for the BRRRR property, not the property used to collaterize your HELOC.
As to your follow on questions regarding DMSH. I believe the DMSH rules only apply to an active business. In my opinion, DMSH is only available to a property after you place it in service; you are not in business until then. i maintain that make ready for rental use costs are always capitalized regardless of whether some portions of the rehab project might be considered repairs. I understand that there is some disagreement among the professionals on this topic.