You guys should be fine to fully fund roth for 2015 (income is too high for traditional) - husband is making 70k, you're making 107k, together is 177k, 401k brings that down to 141k, if you add in bonuses of 8k and 14k (20% of 70k), you're still below the phase out limit
Going forward, in 2016, you have a decision to make:
1) take the 28% tax hit and fund Roth using backdoor method - never get taxed again
2) contribute to brokerage account if you believe that you will be able to get into the 15% tax bracket in the future to take advantage of 0% capital gains, otherwise, you're better off with a Roth since capital gains and interest is not taxed
I find 2 to be riskier than 1, as trying to change grandfathered Roth IRA tax free status is a lot more politically unpopular than raising capital gains tax, YMMV
Your question on taxes - normally, since you're contributing the max to your 401k, your paycheck is being over deducted for taxes, I would have your W4 be married, with one extra allowance, and your husband's to be married, with zero allowances, you may still get a refund at the end of the year this way, but it's preferable to being penalized for underpaying taxes throughout the year