If being struck by the items has left a mark, or marks, on your ds PLEASE take him to your GP today and (no matter how small or trivial they may appear to you) have these non-accidental injuries recorded in his medical notes.
Make it clear to the doctor that this is not the first time your ds has been struck/had items thrown at him by his father and that your ds is being subjected to verbal abuse on a daily basis. Reassure your son that is safe for him to tell the doctor how his father behaves towards him and, if necessary, reassure him that you intend to make sure he will not be able to harm him again.
The doctor will be obliged to make a referral to the police and social services but don't be scared of any 'official' intervention as each of these authorities have the power to require your partner/husband/child's father to live elsewhere pending further investigation of your child's case and, in addition, should it be necessary ss may be able to prevail on the council's housing department to provide alternative/temporary housing for you.
In the event that there are no marks, do please consider taking your son for a general health check as it's often the case that children who are abused fail to thrive and an experienced GP should be competent to recognise the outer physical indications of what is undoubtedly your son's inner psychological turmoil.
Also make contact with Women's Aid, explain your own/your son's situation, and ask for recommendations for solicitors in your locality who specialise in family law and who offer a free initial consultation.
However, please note that evidence of you/your son having suffered domestic abuse or violence should entitle you to legal aid which, in turn, is good reason to make a trip to your GP the first port of call.
From what you've said and without knowing your marital status or who is named on the tenancy/mortgage agreement for your home, you may be advised to apply for emergency injunctions in the form of an occupation order which can enforce your right to stay in the family home while excluding him because of his violence and abuse and a non-molestation order which will prohibit him from coming within a stipulated distance of you/your son.
An occupation order can also set out who has to pay the rent/mortgage and maintain the family home in good repair but both this and a non-mol will only remain in force for no longer than 1 year from the date it was granted, after which you can apply again if necessary.
I can't overstress how important it is for you to be proactive and take steps to prevent any further abuse of your ds NOW.
If you delay it's probable that the abuse your son has been subjected to for far too long will escalate as he grows and if this appalling state of affairs is picked up by his school, or by a concerned neighbour or other party making an anonymous report to SS or the NSPCC, your failure to protect him may cause you, intially at least, to be considered to present as much risk to your child as his father does.
Please don't let it come this - your little boy desperately needs you to step up to the plate and be the exemplary role model his father will clearly never be.
FWIW, if you live in London I know of an approved dog foster carer who may be able to accomodate your pet and I daresay that other dog loving mumsnetters around the UK will rally to the cause in the event that you are required to vacate your home temporarily and are unable to take him/her with you.