Just wanted to clarify - If you were married to the father he wouldn't need to go with you to register the birth, but since you are not married, the father would have to be present to have his name entered on the birth cert - these are the current rules
This is taken from Cardiff county councils website, which is my district but all councils in England and Wales follow the same rules.
"Who can register the birth?
If the parents of the child are married to each other at the time of the birth, it is possible for either parent to register the birth. However, if the parents are not married, the father's details can be entered into the register only if both parents attend together to register the birth. If this is not possible, please telephone the register office for advice.
If the father's details are not entered at the time of registration, it may be possible for this to be done at a later date. "
You may also find this website useful as it outlines who has parental responsibility, who can get it and how and also what it means.
http://www.direct.gov.uk/en/Parents/ParentsRig hts/DG_4002954
If he's making threats I wouln't put him on the birth cert but thats something that only you can decide, you can add him later but you can't have him removed! Good luck. x