Yes. "-I" inserts rules at the top of the list and "-A" puts them at the bottom. You can also specify a position number you want your rule to be placed at. Iptables rules are executed top to bottom. First rule to match a given packet is the one the packet goes with. You sound like you are...
Yes. Setup some pre-routing rules that point ports to your Openvpn port. For example
iptables -t nat -I PREROUTING -p tcp -d {your WAN IP} -m multiport --dports 10:18,64,1053 -j DNAT --to-destination :1194
You can have up to 15 ports with each rule. Ranges count as two ports. If you need...