AWS Sophos UTM (NAT and VPN)

Hi,
Has anyone configure the NAT and VPN via AWS Sophos UTM ? Need help as AWS does not allow public IP NAT, only RFC 1918 compliance (Private IP) subnet can be added for routing
AWS (10.0.0.0/16) -> NAT 7.44.155.0/24->VPN->6.225.55.78 (Gateway -121.224.13.80)
How should approach this ?
1. Create a site to site VPN first from AWS to Remote
2. Create a static route for 7.44.155.0 ?
3. Route 7.44.155.0 to 6.225.55.78 ?
4. AWS server configure gateway to the Sophos UTM server ?

Appreciate your help !

Thanks !