To the questions- Having been a project manager for longer than I care to really think about, I can say that more than half the time the answer to "what can I (the project manager) help you with" the answer was "nothing". The structure of the question focuses it on the project planner, not the problem. The engineer might not even think about his argument with IT about getting lab domain that isn't on the corporate network or how the project planner (manager) can help help them.
Focus on the person. Make it all about them. Make the question more open ended. "What is blocking you from completely your work this week?", "What resources do you need?" etc.
As to the method of asking the questions: Email is a highly imperfect medium. Essentially what you're sending out is a survey. Responses to surveys generally run in the 10% range (and marketers are thrilled if they get this) and those surveys are usually just checking boxes on a screen. Even SurveyMonkey would be better and is still not the best solution.
This is why the daily standup works so much better. 15 minutes, and everyone gets a chance to talk in real time. Here's a hint, it doesn't have to be daily. Do make it less than 15 minutes and it could be more than one meeting. If six people are in New York, get on a phone with them at 10:00am, meet with the guys near you at 9:00am.
With a team of 18, it is not out of scope to be able to touch base with each person twice a week one on one. When I ran the PMO at Hitachi I met with everyone in the core team multiple times a week. I knew about problems before they ever became problems and was able to head them off proactively.