The vpn connecting with either 500 or 4500 only affects the communications for the IPSEC traffic itself and not the encapsulated tunnel. So I don't believe this is related to your issue. Typically a problem with the Nat-T will prevent the tunnel itself from comming up.
By default Juniper attempts to use proxy-id of 0.0.0.0/0 on both sides so that any traffic can go through the tunnel unless you configure more specific ones. This is probably getting the more specific from the negociation with the peer. I'm guess that is non-juniper. Once again, if the tunnel successfully comes up, this is probably not the issue.
Unable to pass traffic on a VPN that is up, is typically related to either routing or security policies. Follow the steps in this kb article to narrow down the issue.
https://kb.juniper.net/InfoCenter/index?page=content&id=KB10093