you have many questions and it looks like you are asking someone to provide all the different conf you may want to use. Well, I can help you with the full conf if you want, just contact me at my email to discuss my servics (firstname.lastname@example.org).
As for your questions;
1. confg pbx using hopoff. In the DX, like all the Gen 2 units, the name PBX and PSTN is removed from the interfaces because you can make either interface do either task (hop-off or ldn). All you need to do is assign a hopoff to a tcrg group and assign the tcrg to the channel group that has the channels of the interface you want to use the hop off on, in this case interface 1 (or as you still call it PBX).
2. pbx 2 pstn is working using hopoff, passthrough is disabled on both ports – I do not see a question in this. You seem to have stated a fact.
3. for only specific numbers go to pbx through hopoff? The problem here is that you are using a SIP proxy. What has to happen first is the sip server has to reject the call that you want to send to the interface 1 (PBX). Once it is rejected from IP, then the tenor will look to other routes to send the call to.