Unfortunately, my FLR (M) was refused today

To start with I am holding a British National (Overseas) passport (aka BNO) while my partner is a British Citizen.
I have made the following timeline to make things bit clearer:
09 Dec 2016 - me granted Entry Clearance as a Tier 5 visa (valid for exactly 2 years i.e. expires on 09 Dec 2018)
10 Dec 2016 - me entered UK and started living with my partner at our current address
11 Jan 2017 - earliest documentation showing we are living together as a couple at the current address
28 Nov 2018 - we went to premium service centre personally to get the application done
28 Nov 2018 - application declined
So as you can see my Tier 5 visa runs out on 09 Dec 2018 which is bang on 2 years from the issue date while the first evidence showing me living at this address is not until 11 Jan 2017. We were told by the officer that they can only count the 2 years from 11 Jan 2017 as there is no evidence that we were doing so before that. And that means we are actually 6 weeks + 2 days short of the requirement of 2 years residing together.
The person dealing with the case is actually quite helpful and understanding. He said it's unfortunate and said we have met everything else apart from the '2 years bit' and my visa would have been granted if that bit is met as well. We were given a few 'options/advices' by the officer summarised below:
1. Appeal against the refusal and hope for the best. And during the appeal process I can still stay in the UK and work legally until the outcome of it. We could also withdraw the appeal when it comes to 11 Jan 2018 at which point our 2-year residing together requirement will then be met. We can then start another fresh application again within 2 weeks of withdrawing the appeal.
2. Get married asap to obtain a marriage certificate. We are told if we had the marriage certificate in the first place then the 2-year residency together will be out of the question and they won't even need to look at it. Then we can maybe start a new application with the certificate in hand?
3. Leave the UK to somewhere else after 09 Dec 2018, perhaps to stay briefly in a EU country or returning to Hong Kong for a bit and apply freshly again from abroad.
Personally we think option 1 would be the best. It is basically paying to appeal and to buy time for me to stay in the UK legally until 11 Jan 2018 at which point the final requirement will be met. Option 2 would be the second choice as we were thinking to get married in 2 years time anyway but will be kind of rushed to get it done. Plus whether we can actually get that done on time as it is approaching Christmas it would be busy, and we will need to book appointment to give the council notice, book venue, book registrar etc... which can take quite a while as I would imagine things are all fully booked until some time next year at least. Option 3 is the worst out of all and we tend not think about that at all as it will make things even more complicated. Well obviously we can do BOTH option 1 and 2 to be the safest but we are thinking only option 1 for now.
Any thoughts and advice on what we should do please?
