You cannot transfer miles from Flying Blue to any other frequent flyer programme, or from any other frequent flyer programme into Flying Blue.

This is a general rule for all frequent flyer programmes; and this is why airlines "partner-up" and instead allow earning in their own programmes even when you fly on other airlines (the ones they have partnered with, at least!). If they were happy to allow miles to be transferred in and out of a programme, then they would most likely have merged the two programmes into one (which, in effect, is what Flying Blue is - the merger of the old AF and KL programmes. The only other example I know of where miles can be transferred between programmes is that of British Airways Executive Club and Iberia Plus - but they share a common currency (Avios) and are both owned by the same group, IAG).

It makes little sense to go to so much effort to determine which of the available programmes will give you the most miles for each sector, if you then end up with multiple accounts with tiny balances in each. Is having 5,000 miles in a "Fortune Wings" account really a better situation for you than instead being able to top up your Flying Blue balance by 2,000 miles (just to make up a fictitious example)? Sure, it sounds like you get more miles if you go with that other programme - but what can you do with those 5,000 miles? Will you ever add more miles to that programme to get a usable amount? If you do, doesn't that just mean you are deciding not to top up your FB account? Does it really make sense to open two accounts in the same alliance when you end up "diluting" the power of both by diverting your Skyteam flying between two, rather than putting everything in the one account?

Beware that if your Alaska Airlines flight is coded anything other than Alaska, KLM or Air France, it will earn nothing in Flying Blue. For flights that are not coded AF- or KL-, they must be coded AND operated by a Skyteam member in order to earn miles (and check the relevant page; for many Skyteam members, all of the cheap economy classes earn nothing in Flying Blue. For a non-Skyteam Flying Blue partner (such as Alaska), in order to earn, the flight would have to be coded AF, KL, or the code of the airline in question (AS for Alaska) and be operated by the airline in question.

If SEA-SAN is coded with a Hainan flightcode, then you will earn nothing for this flight in Flying Blue. (having quickly looked online, it appears that the Alaska flights would be sold with their own AS numbers. On the random dates tried on Google Flights and going through to the Hainan website, you would not earn anything even on the Alaska flights. For me, they book into G and R (Restricted Economy), both of which are excluded from earning in FB.)

Sometimes you just have to accept that you will not be able to earn miles in (any of) your main programme(s).