Your message to him was confrontational and aggressive. Yes you were angry, and i sympathise with the infuriating behaviour from your ex, but your message was only going to wind him up and he was going to retaliate. All you had to say was something like:
I am unavailable to be here prior to 6pm on [date] as I have an arrangement elsewhere on this date. Please do not return the boys before 6pm as they may become distressed and upset if I am not hear to meet them.
I would also like to remind you that the agreement/court order is from [day/time] to [day/time] each week. This is what you wanted and we agreed to in the best interest of the boys. Pleae note, the court order details the minimum amount of time you should see the boys, not the maximum.
Keep all messages short, too the point, and non confrontational. Don't let him get to you. Come here and shout and let off steam all you like by all means!
You have every right to blow off steam and be angry at him over these issues, just try and avoid showing him that he is getting to you, because then you give him the control coz he will threaten to cut the money and you will appear to back down because of that...
As far as money, the CSA can be quite quick in simply straight forward cases where the other party is co-operative. Don't rule them out completely if he keeps threatening to stop the money. If he keeps on like this point out that the CSA is an option if he would prefer to go that route to please contact the CSA to make an official calculation if he feels he really is paying too much then he would be better off doing this surely...
I would also suggest you point him at the CSA website if he continues to threaten to deduct money, and if he does deduct money get onto the CSA right away. It might take a while to get sorted, but it will be backdated.
What he does in his own time with the boys is not covered by his payments, and the CSA would make a deduction to cover this time anyhow when they calculate. Also pants and socks might be considered deductable if you asked him to get them and he gave them to you. If they are for the boys to have at his house then no, they wouldn't be deductable as would be considered part of his costs. And if you didn't ask him to get them then you can say not necessary as you have plenty at home already...
Any money he pays for the maintenance of his children doesn't necessarily include nursery costs. It is to cover housing, food, clothes and essentials. Nursery places aren't a necessity in reality. However the CSA calculation is meant to give the children a lifestyle they could have expected if the parents had stayed together. So if your combined income would have supported this then it should cover some of the cost. If you don't use the CSA then you must agree between you what is covered by teh payments. If you disagree with anything he considered deductable, inform him so in writing (but keep it calm )
Also with nursery fees, you might get help towards this on Child Tax Credit. Are you on WTC? If you're not then do what you have to to up your hours to 16 per week when you will probably qualify. If you don't work then make sure you are getting the full entitlement of free nursery places for your child. If you can't afford them then you might have to look at cutting back on that.
Best wishes
Gilly