It that were me, I personally would:
a) Put all that I can in the 401k until you meet the company match. No more and no IRA. Why no more? (1) You don't have the money and (2) you can get the same return with zero risk elsewhere. If you get a house you'll have loans. Loans that if you pay back more principal, then you need you will pay less interest. A mortgage now is about 5%-6% and possibly a down payment loan would be 7%-8%. Putting your money there is a guaranteed zero risk 5%-8% return on investment year after year. But if you put that same money in the stock market which has been flat for 5 years, you have a risky investment which isn't likely to return more than 5%-8% long term (and likely 0% or heaven forbid losses short term). No risk vs risk. Either way, time compounding of money will leave you financially the same long term. But one has no risk at all. There are minor tax differences between the two options, but at your income the tax savings is negligible either way.
b) While you may be able to afford more, in your situation I wouldn't want to spend more than $800 a month on housing. Of course, I don't know if that is possible in your situation. You are still going to have ~$1500 a month in other expenses, then include your 401k and you've nearly already spend your entire $2500. You'll have no money for fun, for emergencies, or anything else. You can try to skimp and save and be miserable to afford more than $800/month. I just refuse to give advice for people to be miserable for years without furniture in a new house eating nothing but ramen noodles and watching TV with a fuzzy antenna reception. Heck, if you could find a nice home for a less than $800/month I would definately consider it. Note: this number includes principal, taxes, interest, and insurance.
c) Varies dramatically by location, house age, house style, etc. On your limited income, I would definately pay close attention to average gas/electricity bills on all houses you look at. A fancy 100 year old house might run $400 a month to heat in the winter while a charming 20 year old house of the same size may require $80 a month in the winter.
d) To afford a decent house on that budget, you will have to keep these living expenses small. Treat yourself a little though. Don't be miserable. However, learn from some on this forum on how to save on everything you buy. For example, a lunch date at a fancy restaurant may run you $15 while the same date at the same restaurant with the same food for dinner may cost $50. Think about that everytime you buy something. There is always a cheaper way to do the same thing.
e) I don't think you have much left to save. Try to accumulate enough that you can survive for as long as it will take to replace your current job if you lose it. Some jobs can be replaced in a few weeks. Other jobs require many months. So no one can answer this question but you.