Morning
I think that the courts would not remove parental responsibility without due cause ie convicted crimes against children as an example.  I tend to think you’re best keeping ur head down and cracking on with ur child. Later on if the absent father comes back at some point and tries to assert his power as parent (in decisions such as schooling), I don’t think he’d have a great deal of strength given he’s not been there since 8weeks of age. If you’re wanting to remove parental responsibility, then presumably you haven’t tried for child maintenance?
However, if he raised his head later and requested contact then he quite possibly could gain this through court if he wanted, again presuming no safeguarding risk. I think you have to consider your motives for wanting to remove parental responsibility.