limited contact is so hard..... desperate to resond!!!!

So ive had to come straight here, i had to send xN an email to let him know our boy was poorly and isnt in nursery and wont be able to see him tonight. Kept it really formal, he replied 'oh ok, guted i was looking forward to seeing him' i didnt respond to that but he has emailed again saying 'tell j i love him so much and give him a kiss from me, i know u wont but i cant help trying!'

Ahhhhh!! He makes me so angry and sad all at once just having such limited contact feels to much. Im so desperate to respond to him, and say well actually i tell him every day, its not his fault u left and discarded ur family is it. If u loved him u wouldnt let him down, u would pay some money for him, u would be there when he is sick and not scream at his mother saying 'i dont need this emotional bullsh@t' and slam the phone down, u wouldnt threaten to physically take him!

Ive got to be strong i will not respond :-( it makes me so sad this situation, i never wanted this for my boy ever.