It's not "long resolved" if you were drinking enough when you fell pregnant to need a slow alcohol reduction. How many weeks are you?
It will be in your favour that you were honest at the outset, have sought medical advice and followed the advice too. Unfortunately a pre-birth is necessary as your abstaining from alcohol is recent, and as the baby isn't planned there is understandable concern that you may resume drinking in the near future. You know how you feel inside and how likely that is, but obviously SS have to be prudent in this kind of situation - everyone says they will stop drinking but of course not everyone does, so SS have to be as sure as possible.
I personally don't see why you can't see the referral.
I would advise you to be careful and choose your battles. There is no point nitpicking on ultimately irrelevant details. I appreciate that your level of alcohol use is an important detail and something to clarify though.
Your SW should record your views, there should be a section on the report for that. It is unlikely she will change her assessment (unless there are clear factual errors as opposed to opinion) but your views can be included.
The 45 day deadline is a maximum amount of time, not a time to aim for if that makes sense. If she is able to complete it well within that timeline that suggests she is hopefully quite efficient and not overworked, which is good.
Try not to feel that SS are against you. Truly, they don't want to remove babies. I have had to do it, and it's horrible, and you so want to help families fix things before that point. It really is an awful last resort.
The main thing they are looking for is that you understand the gravity of your past drinking problem, you understand this is a concern (again I appreciate that you no longer feel it's a problem, but objectively/on paper this needs to be seen by SS to be believed). If you minimise your past issues they will be worried that you don't think it's a big deal and are therefore likely to return to that behaviour. I'm not saying that is how you feel, I'm just trying to make you aware of how things could be perceived - remember these people don't know you and can only go on what they have.
Follow all advice, attend all appointments, connect with your bump, prepare your home - show you are putting your child first, before everything else, including alcohol.
A pre-birth is an assessment at this stage, nothing more. The result of it will be
A)no further action, case closed
B)a child in need plan
C)a child protection plan
D)possibly support via an 'early help' team if they have them in your area. This is lower level support.
Options B, C and D will have a plan generated for you to follow, with clear expectations. You will be involved in the making of this plan. It should be clear what they want to happen in order to help you make changes.
Sometimes in the child protection arena if things are very bad they may also start court proceedings alongside this but you should still have a clear plan to follow. If it goes this route you will get legal aid if needed.
I hope this is useful. Don't want to scare you with court, just giving you all the potentials. What you've said doesn't sound like it's there, but can never know from one post.
Good luck in your pregnancy.