While I'm still hoping the sentiments are adjusted, especially where toddlers are concerned, I may have accidentally stumbled upon a workaround if you're not averse to using cheats. I don't know what the policy for cheats in TS4 is, considering it is a stand alone game and we're not in competition like other kinds of games, so I hope I don't get into any trouble for this. However, if the game is buggy and toddlers are basically ruined and my only option is to use cheats, then I guess I'll take my chances.
**If you decide to try this make sure you save your game first: Go to the menu and select "Save as...". Name it something else like "My Game Test" for example. This way if the below doesn't work, then you won't lose any progress in your existing save.
1. Enable cheats
2. Shift+click on toddler with unwanted sentiment
3. Select "remove from family"
4. Find toddler in parent's relationship panel
(Note: You may want to click on toddler's avatar and "Open Sim Profile" to double-check negative sentiments are gone)
5. Click on toddler's avatar and "invite to hangout at current lot"
6. When toddler appears at lot, shift+click and select "add to family"
Details:
I had another toddler who got "hurt" when he didn't want to be potty trained. I played roughly two sim weeks having the dad interact positively with the toddler; reading, playing, tucking in, etc. Finally, I again got frustrated but this time I used the shift+click cheat on the toddler to "remove from family". This removed him from the household but not the game. I didn't know that would happen. I saw the toddler in the dad's relationship panel. The dad still had "adoring" and "growing closer from quality time" sentiments but the toddler no longer had the "hurt" sentiment. I was able to invite the toddler "to hang out at current lot". As soon as the toddler showed up, I used the shift+click cheat on the toddler to "add to family". The "hurt" sentiment is gone and the dad can interact with the toddler who no longer is sad or angry by his presence. I've only done this once, as I said purely by accident, so I don't know if it will work every time but hopefully it helps others who are suffering as I have been.
PS - One theory I have based on the above is perhaps the "hurt" sentiment is getting stuck somehow and removing the toddler from the household cleared it. Since the "hurt" sentiment is supposed to be short term, it should not last longer than a couple of sim days. Other short term sentiments like "smitten" and "closer from happy memories" come and go regularly and quickly, so should the "hurt" sentiment.
