Interesting posts. I am an electrician, (licensed Master for 40+ Yrs) A few things to note. 1st: Aluminum wire is fine, as long as your connections are rated CU/AL. (They will be labeled). Also be sure to use an anti-oxidant sealer at all Al. connections. Supply houses have it, also big box home stores. (HD, Lowes etc), Note also that modern Aluminum used in wire has been alloyed to be reliable for use in these feeds. (As opposed to the older wire which gave it it's bad reputation) From your description both panels (Home & Garage) are considered "Sub Panels", and require the ground to be isolated from the neutral at the panels. Neutral and grounding conductors are only bonded at the Service Point, which in your case is the pole, and the 200 amp panel referenced. Separate ground bars are available where you purchased your panel, and your house panel should have the grounds isolated also. Remove or do not install the included green bonding screw that comes with the panel. The Main Panel at the pole will need this "bonding jumper installed". (only at this panel) At least one ground rod should be at each at each of the three locations. Separating the grounds prevents "Objectionable Currents" from flowing on your grounding system.
Have fun! R.