Sorry about the PFS, you are correct I misread the proposal listings there.
As far as the proxy-id are concerned, these are explicitly configured on the SSG140 side so would need to remain on the SRX or be removed from both.
set vpn "Dallas_VPN" proxy-id local-ip 172.16.10.0/24 remote-ip 172.16.72.0/24 "ANY"
The other configuration I notice on the SSG140 is enabling tunnel monitor with the default settings. I have had issues with this combination if the remote side is not also an SSG firewall. I would either remove the setting or change this to use ping to a specific remote address from an interface on the SSG140 that is in the local proxy-id subnet.
Also if the status of the IKE and SA could be grabbed on both sides during the issue these might be helpful. I see the IKE in some of the above but not the SA.
SSG
get ike cookie get sa
SRX
show security security-association ike show security security-association ipsec