Losing my TA-ship, need advice
Most graduate programs try to be more transparent and forthright about TA funding than seems to be the case for you. That is, at the outset there would be promises made about number of years of funding, conditional on reasonably good performance in coursework and teaching. Departments are very well aware that grad students will have difficulty surviving (much less paying tuition) without financial support, so do not usually cut support without considerable prior warning, explanation, explanation of terms for reinstatement, or explanation of economic conditions and prognosis for future funding. To do otherwise is irresponsible.

I do have to wonder whether you were paying attention to disclaimers about fragility of funding, though, too. For that matter, do you have a copy of the TA offer letter? It really should spell out what you can expect in terms of funding. For that matter, no one's advisor should be "the last to hear" that their student(s) didn't get TA funding renewed.

Of course, it might be that the central administration at your university "pulled the rug out from under" your department, and the budget changed abruptly and somewhat catastrophically. But, still, I'd think you would hear something about this, an explanation, rather than just a passive non-support situation arising.