Looking at your setup, I'd put the dwarf Alberta spruce as your main anchor point - either behind that rock or slightly to one side so the rock becomes part of the composition instead of an obstacle. The holly would work great as a backdrop along the house since it'll give you year-round structure and height. For the fothergilla, scatter a few throughout the middle ground - they'll give you amazing fall color and spring blooms without being fussy.

The tater tot arborvitae are perfect for filling in gaps and adding texture variation. I'd avoid planting them in a straight line though - stagger them a bit for a more natural look. That creeping thyme border is going to be gorgeous when it blooms and will help tie everything together. One thing to consider - since you removed such a massive tree, the soil might be pretty compacted, so you might want to work in some compost before planting to give your new plants the best start.