Assuming you have your passport, if you attempt to visit the most likely outcome is that you just go through an automatic passport reader gate, and never talk to an immigration officer.
However, there is a small potential risk. By applying for a settlement visa you have indicated you are able and willing to move to the UK, increasing the risk of overstay. ...
IANAL but I see no easy long-term solution to your situation unless you resolve your marital status.
You cannot apply for a fiancée visa because to do so you would need to prove that your marriage has ended and that you plan to marry or become civil partners within 6 months of arriving in the UK https://www.gov.uk/uk-family-visa/partner-spouse Although you ...
No realistic answer can be given to this question due to the amount of unknown factors at present.
Until the legislation passed in known after a Scottish independence, one could only speculate.
So any speculation now, would not result in an answer that one could rely on.
Policy on locations from where applications may be submitted is set out in the UK Immigration Rules Part1 (Entry Clearance, section 28) https://www.gov.uk/guidance/immigration-rules/immigration-rules-part-1-leave-to-enter-or-stay-in-the-uk
An applicant for an entry clearance must be outside the United Kingdom and Islands at the time of the application.