I am not an expert 

but If I had your project and wanted a lot of speed for not a lot of $

I would be incline to:
* get a spool of direct bury cat6 cable Example: 500 ft of cat6 is $110  amazon,   rent a machine to dig a trench (home depot) and direct bury cat6 line between buildings.
* get a crimping toolkit to make your own cat6 network ends  $20 amazon. 
* get a 5 port switch for home so you have ports to click cables into: TL-SG105 $15 amazon
* doubt you will use the starlink router.

Because the above uses Cat6 for all backhaul [both within house and between buildings]
I think the cheaper dual band M5  will be as performant as the tri band M9. 
A 3pk of M5 is $150 amazon. you will need 3 units min ...
put an M5 each outbuilding and 1 or 2 in house as needed (use the ethernet of house to connect its M5's)

The primary advantage of the above is all 3 buildings are guaranteed
to enjoy the same internet speed as every other building and all should enjoy perfect wifi.

If ditching is not an option.  there is still a chance of success.
forget M5 use M9 everywhere.
A 3pk refurb M9  is $213 amazon sku:B07ZPCVNNV  
I think you will need 4 units min possibly 5
one in house window facing garage(using window to try and minimize wall interference)
one in house window facing cabin  (using window to try and minimize wall interference)
(There is no guarantee a that a given  building will dedicate itself to one unit but we are trying to present each building an "idle" m9 for it to talk to)
Place the garage & cabin M9's in  window facing house  (using window to try and minimize wall interference)
you may find you need an additional M9(s) in house to service the house      

all M9's in house should be connected via ethernet 

this 2nd option won't be as performant as the first option but has a chance of working for you.

if you want to try and "future proof" yourself bit do option 1 but use m9 so you have options for future.
Good luck.

@OracleDBA 

thank you for the ideas!