"There is only a finite supply of investment grade mortgages out there, so by buying all of the good ones up, the Fed is leaving the market riskier and less liquid."
So here is where I don't follow you. I don't see how the market can become both riskier and scared of lending. There is a fixed amount of agency backed MBS by Fannie and Freddie, and the Fed is buying up a big share of them. Presumably that means that prices on other types of bonds, riskier bonds go up because investors are putting their money in other types assets like commercial banked mortgage securities , etc. If that's the case then doesn't that mean that investors are less scared of investing and lending out money? I just don't see how, if the market is purchasing riskier bonds, that that means there is less money being loaned out.
Presumably if the Fed did not do this then mortgage interest rates would increase because the yields would be higher and the price of the bonds would be lower. If the housing market is deemed to be key to economic recovery, I don't see we'd want interest rates on mortgages to increase.
"And it's my opinion that much of the change going on in the labour market is structural rather than cyclical. "
If long-term unemployment rate of over 4% is structural then our economy is not going to recover. That's a catastrophic number if we can't bring it down. Never before have we had such a high long-term unemployment rate. I'm unclear as to what the evidence is that it's structural, especially in light of the fact that we're engaged in a policy of fiscal consolidation rather than stimulus, taking government money out of the economy instead of putting it in. There is ample evidence to suggest that employers simply do not like to hire anybody with any kind of gap in employment history. In fact, although this is anecdotal, I've been told as much by an HR staffer for Nationwide Insurance.