Thanks for the pics. On the steerer tube measurement, you want the full tube length down to the fork crown as opposed to the newly-added crown race. The crown race is 3.5mm thick at the flat faces so your full steerer tube length is actually ~232mm.

Your ideal steerer tube length is 176mm + 45mm = 221mm, as you correctly calculated, but as you are measuring from the new crown race you'll actually want that measurement to be ~217mm (subtracting ~4mm for the crown race thickness), or 11mm of steerer removed (roughly the same as that spacer thickness, not by coincidence).

As far as the tightness threading on the upper portion, if you've threaded it on to the end at least a full couple of turns by hand and the threads are visibly clean, you can be confident that it is not cross threaded. At that point, you can clamp on a threadless stem which will make further threading (including the bearing preload adjustment) *much* easier. Always get those first few turns by hand, though.

For reference, the upper portion will thread over ~27mm worth of steerer tube before the steerer bottoms out internally. Don't try to force it more than that but it will need to go that far to preload the bearings so get a sense of what that feels like. Depending on how clean the tube ID is and how concentric its threads are to that ID it can take some additional torque to get it there. On my Trek 660 that was definitely the case but other bikes have only needed extra torque at the bearing preload step.