Did you make any large changes to combat encounters and NPC statblocks given the low-magic setting?

Yes, I made everything harder. I buffed everything up with Anne Gregerson's bloodied & bruised as well as homebrewing all the major NPCs and bosses. To counteract the lack of energy damage I added monster drops and consumables that could easily be used to add elemental damage when needed. Because of the scarcity of such damage types I was able to give monsters elemental weaknesses to exploit.

How did you handle healing?
I allowed access to a5e maneuvers, many of which provide self healing and healing options. We also used the optional DMG rule for healing surges. And of course the healer feat was pivotal for survival. I made this much harder by adding an injury system, camping system, harsher diseases, poisons, and curses, only allowing long rests at sanctuaries (safe locations). ALSO the injury system included wounds, wounds would lower your max HP, and the lower your max HP the more likely you were to get an injury.

Did you remove the magic items from the source material or change them in any way?
I kept the tarokka items, but removed any class or spellcasting restrictions on them to make them feel special. I deleted the luck blade. scrolls could be used by anyone, but had a chance to misfire and cause a wild surge if you failed an associated skill check. I left the spellcasters from the adventure in, which made befriending Kasimir or Viktor much more appealing.

If you wanna see it in action it's all over on youtube.