Your understanding of the situation is very different from mine. Obamacare is not funded in years going forward. Each year Congress must pass a budget that authorizes spending for various programs. If they do not vote to fund something then it is unfunded. Thus there is no need for Congress to pass legislation and for Obama to sign it to de-fund Obamacare. They need only to not pass legislation funding Obamacare. The Republican House majority is sufficient to accomplish this. A spending bill that includes Obamacare funding need never reach the Senate.
You may be right. But if a law is already passed, which stipulates spending x amount of dollars along its span, how can the new congress reverse that without passing another law?
Are you saying that a law already authorizing expenditures is meaningless unless approved each year by the congress?
Any new bill to stop funding will be vetoed by Obamao.