Do nothing inflammatory. Do nothing at all.
Learn to download the text messages onto a computer or if that is too hard, just write them into a diary. How many kids and how old? When are you meant to pick them up next and from where?School? Her place, etc.?
Look, I kind of think talking to your solicitor might be a waste of time, atm. At present, all she is doing is threatening to withhold the children. There is nothing you can do until she actually withholds them and it is likely the solicitor will say the same.
But you should write to the ex to tell her that you expect her to comply with the court orders.
Mate, sounds like you have a long battle ahead. The ages of the kids are likely to be the most important fact in this case
Just stay calm and look after yourself.