Ex trash talking me.

Yes bjane02 agree with MOnica keep your dignity your ex is the loser ,your daughters have your good example to follow which will keep filtering through .The spoon feeding of gifts,‘affection’ to your eldest,using her as a financial prop but verbal abuse to you by him via her will surely back fire in time one day.
Your eldest must feel deep down that all this trash about you can’t be true and see through him it ll take one slip and she ll realise .
They will all see for themselves one day what a sad manipulative man he is but they ll love and respect you .
What goes round comes round .

My ex did this to me. I protected my children from him when they were growing up so they didn't know about the things he used to do. I stayed until they were 18 and 21. The eldest had left home and, although I wanted her to come with me, she chose to stay with her dad. He then proceeded to fill their heads with all sorts of rubbish. They believe that I was a spendthrift who was having multiple affairs and goodness knows what else. He, of course, was a martyr to my behaviour. They don't know that he was a drug taking, womanising (including working girls) alcoholic. If pushed they'll accept that he's a 'heavy drinker'. I've never told them what he was like because I chose to protect them and don't see what good will become of bad mouthing their father. Causing rifts between children and parents might be his way but it isn't mine.

I would leave the oldest and your ex to it. Your oldest is an adult now, and there’s no reason for you to be having any communication with your ex.
Make your life with the younger two, and encourage them to give the other two a wide berth, for all your sanities.
You neither want nor need this, so don’t accept it a minute longer.

I think what you need to do is open up a space between your two younger children and you and their father and elder sister. The younger ones should not have to listen to this kind of talk and they are clearly not happy with it.

Secondly do not begin to believe this talking you down. You are clearly doing a good job with the younger ones, who are telling you what is happening which is a sign of their trust and love for you.

I would also stop trying to buy your elder daughters love. It will not work and she will think the less of you for it.

I would not break off relationships, with father and daughter, but open up a gap, see each other less, do not let them in the house, always talk on the doorstep. Discuss the situation with the younger children. See how they would like you to act.

Keep your dignity and do not retaliate no matter how much the temptation.

Does your eldest realise her dad is financially abusing her over his mum's mortgage? It might be time to tell her a few home truths about her dad's behaviour.