3. You should, without a doubt, get some revolving debt in order to help secure the best mortgage terms down the road, unless your wife will be applying by herself for the mortgage. Mortgage lenders will use the lowest of yours and your wife's middle credit score. So if your middle is a 640 and hers is a 740, that would cost you about 2.75% (of the loan amount) additional in closing costs. So you need to get your credit score as high as possible.
Just curious: What are the pros and cons of applying jointly? When my wife and I bought our house, I had both the credit score and income to carry the whole loan myself. My wife's score wasn't far behind, and we applied jointly partially so it would bring her score up a bit.
Really it just depends on the situation. If Spouse A has significantly better credit than Spouse B, and Spouse A can afford the home on Spouse A's income along (debt ratio wise) then they would save significant money in closing costs. If both Spouses have similar credit scores, and nothing funky going on with income, then they could apply jointly.
Basically what I look at, is trying to find the cheapest and simplest route to get the end result. So if one of the Spouses is self employed, which raises the possibility of the underwriter to raise additional questions or require additional paperwork, then I would advise to do the loan in just the W-2'd spouses name (assuming they qualify).
Each situation is different but that is the nuts and bolts of how I make my recommendations. Try to keep it simple and easy.