the first mistake you make was that you only applied to only 3-4 universities. you should have applied to 8-10 universities with few universities that you can easily get accepted just to hedge the risk of not getting accepted into a good school that you wanted to go. anyway, it's too late to talk about that now. my best suggestion is to talk to your adviser or dean of the university where you graduated to see if you can get admission there. give GRE test again and transfer to different university of your choice.
or wait and give GRE one more time and apply for fall.
again, i am giving you this suggestion based on the assumption that you were rejected because of low GRE score.

and sorry, i have no idea about assistantship in statistics.

anyway, good luck