MPLS and Internet traffic splitting

I had a company network using MPLS  with IP address 172.16.x.x on Fortigate 100D WAN 1. It is mainly for ERP and VOIP phone systems.

I like to implement another broadband internet connection just for internet access. This new internet connection is not a failover link, it is mainly to prevent the MPLS from overloaded with internet bound traffic.

Question 1: How should I connect and configure the FG100D so that users can use their IP phone and ERP via the MPLS and surf the internet via the new internet circuit?

Question 2: Can I use 192.168.1.x for the new internet connection?

Thanks.