When I moved to a new area, a HV came to visit us.
DS was 18 months. She raised an eyebrow when I said I was still BFing DS, mostly as part of his bedtime routine.
She asked if I needed any help or found anything difficult. I said sometimes DS was hard to get to sleep.
At this point she pounced on the BFing, told me DS was having trouble getting to sleep because BFing was making him too full up, like eating food just before bed. (This is total bollocks by the way.)
It was striking that she didn't ask anything else before blaming BFing - no questions about where he slept (in my bed, bet she would have been horrified!), how many layers he wore, if it was noisy, what his bedtime routine consisted of, or anything else that might impact sleep.
HVs receive very little training on BFing, but still I would hope she knew that the World Health Organisation's advice is that all DC should be BF until AT LEAST two years old, and that 18 months is perfectly normal.
This is the kind of shit that natural term BFers have to put up with. Issues are ALWAYS blamed on BFing and on the mother. There is huge pressure fir mothers to stop BFing unnecessarily, from when babies are quite young.
The issues are is the trantrumming and the ex's attitude towards parenting his child. This is what the OP needs support with, not a load of people who don't understand that their aversion to BFing older DC is purely cultural and not in the best interests of the child.
FWIW, the reason my DS found it difficult to sleep was likely linked to his autism..We didn't find out he was autistic until a lot later though.
I don't know much about severe tantrumming, so I don't know what advice to offer. I know that BFing isn't going to be the root problem though.