I think the general rule of thumb is mortgage = 3x income. so a $850k+ mortgage is a bit of a reach.
So $250k gross, minus $37.5k from 401k (assuming 2 spouses working), your take home is about $12k a month give or take?
Napkin math tells me on a roughly $850k 30 year mortgage, payment is about $4k a month, but potentially a bit more. Is the $350k ALL your savings besides 401k? Can you keep the house running for a few months if one spouse looses their job?
I personally wouldn't do it due to me being extremely conservative and would rather keep the mortgage below 500k.