Now is surely the moment that Rob and Ursula’s abduction of Henry pays off. At this stage Rob doesn’t need to demand custody of “Gideon” and remove him permanently from the pernicious influence of the Archer family. That is, of course, the long game, but at the moment he just needs to get access and work from there.
So here’s a plan. Threaten that unless he is immediately allowed access he will return to his old job in Canada taking Henry with him, and once he has custody, which he surely will given Helen’s patent unfitness to be a mother, “Gideon” as well. Helen will never see either of them again.
Of course the ultimate goal is that Helen and all her family will be cut out of their lives anyway (or he might just dump Henry once he’s got his proper, blood son) but Helen doesn’t need to know any of that at this point. The Archers need to wake up and realise that he and Ursula are playing by a totally different set of rules to them.
Hell hath no fury like a psychopath rejected!