The US dollar will not cause a market crash.  A default on or a downgrade to US debt is what may cause a collapse.  Absolute worse case scenario is a default situation where interest is not paid on Treasuries.  Odds of this happening are very VERY small.  Even without an increase in the debt ceiling.  A downgrade is much more plausible.  A raise in the debt ceiling has a fairly good chance of happening.  It would be a self-inflicted wound to do otherwise.  However, S&P says they need to see cuts of $4 trillion over the next 10 years in addition to the debt ceiling being raised in order to prevent a downgrade.  This may be harder to achieve as both plans in debate do not cut to this magnitude.

How do you protect yourself in a market crash?  Keep your money out of the market.  How do you make money in a market crash?  Short the market, buy gold, buy treasuries, maybe even play the VIX.

As for inflation, I see no signs of "runaway" inflation at this time.  In the end, I think Congress and Obama will just kick the can down the road.