It's actually surprising no one has questioned the $400k range for the home, especially given the relatively small percentage down ($30k or so, so maybe 10%). Where are you looking to buy? Would understand $400k in most big cities, not as much in suburbs or rural areas.
Also, in your situation, I would generally recommend focusing on improving your Mustache, saving as much as you can of that six figure income and put down something closer to $100k after a year of saving, but in today's market with interest rates low, I would understand a little concern that interest rates may go up some in the next year.
When we did it, we trusted the referral of our agent, which worked out fine but it became apparent late in the game that you have to play lenders off of each other to get the fees reduced and terms improved. Our lender backed off of a number of line items when we showed them a competing offer.
Since we bank partially with Chase, it was tempting as well to take their offer since they offer 1% back on the mortgage if you're a Chase customer. Doesn't mean you shouldnt take the other offer if it's better elsewhere, but I bet other lenders offer deals like that.