Advice required creating a business plan for a VLS-TS visa application

I’m currently residing in the UK and just starting my application for a VLS-TS, AE / Profession Libérale.

My primary skill and business for the last 25 years have been book and magazine design and production, and this is something I will continue with, primarily with UK clients, while actively seeking clients in France too.

Additionally, I am a web designer/developer and create a small number of websites per year (mainly for publishing clients).

However, my current primary source of income is through acting as an agent and all-round assistant to a UK-based author. This involves entering her work for literary competitions, finding her readings at festivals and events and acting as a publisher and designer for her own work. This is a long-term, financially viable project with no time limits, but for obvious reasons, I can see that this might not be a role that presents itself as a feasible activity for a visa application.

a) Would it make more sense to present the design elements of my work as the primary feature and list the other agent-like roles as secondary, or will I have to prioritise where the primary source of income is generated?

I also have two related questions, but I can ask them in separate posts if I’m being too presumptuous; 

b) The French visa website states that I must produce “Documents proving the capacity of the activity to provide a level of sufficient resources at least equivalent to the minimum legal wage in France, corresponding to full-time work.” which I presume will be UK tax returns for the past X number of years. So if I produced, e.g. 2 years of returns, do they both have to match the SMIC amount for the current year or can last year’s return match last year’s SMIC etc.? The reason I ask is that I doubt my previous year’s income will match this year’s SMIC, but my income is increasing, so this and future years’ income will surpass the SMIC level.

c) Even If I can prove that my business idea is viable, do you think the authorities will also require me to show a level of savings? There’s a lot of contradictory information floating around, and I have read this will be a necessary requirement.