Hello – I purchased an older home last summer southwest of Minneapolis (zone 6).  The original slab on grade portion (1 story, vaulted ceilings with no attic – about 1100 sq ft) was built in 1956 (includes 1 office, a bedroom/bath, living room, kitchen).  An addition was added on one end of the home in the early 1980s – additional family room, laundry room, and upstairs bed/bath – about 800 sq ft).  There is a boiler room below a portion of the addition (about 7 feet tall, concrete ceiling), with a crawl space under the remainder (about 3 feet high).  The house has hydronic baseboard fin heat and no air conditioning.  There are two zones of heating – one that covers the original area, with a second that covers the addition (including the boiler room and crawl space)

I’m beginning the renovation journey and would love any and all guidance/thoughts on what I’m consider.  Thus far I’ve ripped off all of the old siding and housewrap – I’ve flashed around all windows/doors, filled obvious gaps, re-wrapped the house, and re-sided.  However, there’s a lot left on the journey as the entire layout/house will likely be touched.  Given the layout changes and my desire to use most of the wall areas for cabinets or furniture, I would very much like to get rid of the baseboard fins – they are old, noisy, and would need to be replaced soon regardless.  Thus I’m considering retrofitting in-floor radiant heat (there is no current ducting and the home design really doesn’t allow for it easily).  The boiler is natural gas, was replaced in 2014 or 2015 – runs with a glycol mix.  I have a separate gas water heater. 

My questions: 
– should I consider a air to water heat pump that handles heating and cooling?  If so, would a ERV and/or dehumidifier be sufficient to prevent condensation on humid summer days?  Would I be able to tie-in the existing boiler to supplement heat on cold winter days?  Are there any straightforward guides on how to design the in-floor radiant system?
– As I renovate the home I expect to find 2×4 framing – what types of insulation should I use?  I’m considering spray foam as I’m intrigued by the vapor barrier properties (I’m quite certain areas of the home are not sealed properly – especially the upstairs ceiling). 
– for the infloor retrofit – I’ve read I should add vertical rigid foam insulation on the outside of the slab.  If I added horizontal rigid foam above the slab (inside) but below the PEX, and also spray foamed the walls, is there still benefit to adding the vertical rigid foam outside?
– if a heat pump doesn’t make sense, I would consider mini-splits for cooling.  Is it better to go with one large unit and run longer refrigerant lines, or should I install two units to limit the line runs (the way the house was built makes it long and skinny – please see layout)?

I apologize for the long post – any assistance would be appreciated.  Thanks.