Locking down iOS devices
You cannot disable Apple Maps. iOS does not provide a method to do this.

The best free MDM tool I know of is Meraki (aside from Profile Manager itself). However, I'm not 100% convinced it will do everything you need. Also Meraki was recently purchased by Cisco and I am a bit concerned about its future. You will also receive sales calls from their staff trying to sell you on additional features.

To accomplish your objectives on the cheap, I recommend looking at AirWatch. We use this in our enterprise to manage several hundred iOS devices and it works quite well. There are other tools that can do this as well. A great full-featured guide to MDM differences is EnterpriseiOS.com.