Jack is getting in between us.....

 Maybe you started giving Jack more attention when you and your DH was having a little trouble. And now you arent?

And just wouldnt allow him to do whatever it is you dont want him to do. Make him leave the room if you dont like it or make him go back and lay down on his spot. Give him a kong or something to occupy his time?

 Bugsy gets anxious or excited (not sure which) when DH & I hug and will try to get between us.  We have hugged with the sole intention of practicing this with him and letting him know he should be invited to join us. Can't say it's perfect but it is MUCH better than it was.

I would teach him where you want him to be instead of telling him where not to be

Bugsy isn't allowed on the bed so that problem hasn't surfaced - in your position I would remove bed priviledges until he understands he must be invited.

I have no expertise in why he is doing this but think it's a pack thing - and I know someone with another male dog that acts similar.  My friend's female golden can behave in a similar manner too so it likely isn't gender

Anyway just teach him to lie down away from you and stay away until invited.  I would think if he does stay away then invite him then send him away and once he settles invite again.  That way he realizes that staying away is more likely to get him what he wants than just barging forward.

Good luck I really do know what a nuisance it can be.  B drove us nuts for well over the first year we had him with this 

Yup, Apollo tries to get between me and Jeremy when we're hugging, sitting on the couch, laying in bed. When we play wrestle he gets super anxious and will get in between us, and then lean on me. We call it "the jealous boyfriend syndrome". I spend 90% of the time with Apollo, Jeremy only spends 10%, so I figured that's why. A Lab breeder we boarded Apollo w/ once said it could be because he's a male and I'm a female, and sometimes male dogs are just closer to female humans- but I don't know how true that is. Honestly, Jeremy works so much (1 of the reasons we got Apollo for me) I don't mind.

Bevo used to do the same things, except that his protectiveness of me would escalate to a point where I was truly concerned for the safety of my, now, DH. 

We got this problem under control, first by removing bed privileges.  This worked to an extent, but soon he decided that he would sit at the side of the bed, stare at us, & growl when DH got too close to me.  I then started sending him to his bed before any extraciricular activities began.  Bev, then decided to growl from across the room.  When the growling started, Bevo was relegated to sleeping in the living room.  (For Bev, being separated from his person, in this case me, is a fate worse than death.)  Along with being kicked out of our bedroom, we got even stricted with NILF, & DH took a larger role in caring for Bev. 

Bev was left to sleep,alone, in the living room for a little over a month before he learned to be more respectful towards DH.  When we first allowed him back into the bedroom, he had to stay in his bed.  Any extra attention or noise of any kind landed him back in the living room.  Now, he is, again, allowed in our bed.  He has his own corner of the bed, & he knows that if he ventures away from his corner that he will be kicked off. 

 For us, it was a resource guarding issue.  I was the resource.