Your solicitor has given you sound advice to withhold contact (deny access) and wait to see if your exp makes application to the family courts
Residence and contact orders have been replaced* by child arrangements orders. As your exp is named on the birth cert he shares parental responsibility for your ds with you and he can apply to the family courts for a child arrangements order as can you, but at the present time there is nothing to be gained from you making application.
Please be reassured that, should he make any such an application, he will first be required to attend a mediation and information assessment meeting (MIAM) and at that time you should discuss with your solicitor whether, in view of his harrassment and attempted assault, she advises you to attend.
Your solicitor has given you sound advice to withhold contact (deny access) and wait to see if your exp makes application to the family courts and you are best advised to have no further communction with him. If he seeks legal advice he will be told that he can apply to a contact centre for supervised access to your ds. It isn't your place to advise him, nor should you attempt to do so as he can find this information for himself.
Keep all of the texts/messages he sends you and call the police if he turns up on your doorstep or attempts to harass you outside of your home. It would seem that your solicitor is applying for a non-molestation order with an order granting power of arrest and once you have the order the police will have no excuse reason not to arrest him if breaches it.
If you do not have a passport for your ds I would suggest you apply now as it will establish a) whether your ex has applied and b) go some way to prevent him from taking your ds out of the country. If you apply for a passport for your ds your exp will not be able to obtain another. If your ds has a passport make sure it is kept hidden in a safe place - i.e not in an unlocked drawer.
In view of your concern that your exp may attempt to remove your ds from your care and possibly remove him out of the UK, in the absence of a childcare arrangements order I would suggest you talk to your solicitor about applying for a prohibited steps order to deal with this issue.
Your exp's contact with your ds has been irregular to say the least, and the manner in which he has demanded to have contact when it suits him, including overnight stays for such a young infant, shows little concern for your ds's welfare and his need for consistency. Does he pay child maintenance regularly?
It seems to me that you've allowed yourself to be bullied by your exp into letting him have his own way to the possible detriment of your ds, who now needs a prolonged period of peace and calm to recover from the trauma caused by a highly upsetting incident in which his father attempted to strike his mother while he was in her arms and take him from his home.
It's in the very best interests of your ds for you to stand firm and follow the advice given to you by your solicitor. As your exp is one of those who given an inch will take a mile, you must guard against allowing anything he says to cause you to lose confidence in your ability to do what is right for your baby and, needless to say, you should never let him in your home again. Do you have a supportive family or friends who can stand shoulder to shoulder with you?
Your ds will most certainly not grow up to hate you for protecting him from his father's excesses, but he may come to despise you if you don't.
*those who have these orders do not need to re-apply.