However, my husband is not answering any phone calls and I have a feeling that his family is upto something fishy. Is there a way in which he can cancel my PR card as it is his sponsorship?(MY PR card is with me)
Your husband and his family may think they can cancel your PR, and they may tell you that they are going to, but there is nothing they can do. You are a PR now, and if you stay in Canada long enough in every 5-year period, they cannot take your PR away. However, if you lied on the application forms, and your husband reports this to CIC, then you could get your PR taken away. If so, it will be a long process, and you will be able to present your side of the story. Usually CIC does not bother following through with these reports: they don't have enough staff, and they know many reports of fraud are just a vindictive ex-spouse trying to make trouble. You stayed together for a while, so it does not look like a marriage of convenience.
Is there any rule that I must re-enter the country within 6 months after my first visit out of Canada to keep my residency status?
No. You must be in Canada for 2 years out of every 5 to keep your PR status.
Is there a way in which the government can support me and help me settle down in the country if this end in a divorce. I was working with RBC but currently am unemployed.
You can go on welfare. During the first three years after you landed as a PR, your husband will have to pay the government back all money you get on welfare. However, welfare pays very little. You are better off trying to get a job. There are various programs in every province to help people with low income - which are not considered welfare. If you get divorced, your husband may have to pay you alimony. Get a lawyer in Canada to help you with the divorce.