I'm a novice when redeeming my FB Miles as I've only done one redemption booking before and that was all easy, so this might be obvious to folks here.

I'm starting to plan an autumn holiday and I'd like to visit Shanghai and Osaka, as only been to both before for airport transfer at PVG and flying into KIX for the train onto Kyoto. So I thought I could redeem my FB Miles on a multicity ticket and for Shanghai get a 240hr Transit Without Visa (TWOV). My dates are not fixed, and I was thinking something like this would be easy (but maybe expensive as from the UK so would swap LGW/LHR for a cheaper start/end city e.g. AMS):

• LGW(1st choice) or LHR(2nd choice) - KIX via PVG with China Eastern in business class
• KIX - PVG with China Eastern or Shanghai Airlines in economy class
• PVG - LGW(1st choice) or LHR(2nd choice) with China Eastern business class

I have a few questions:

• Do flights cost the same if booked as a multicity ticket or booked as a bunch one one-way tickets? I can search the KLM website for one-way redemption tickets but not multicity, so cannot find the cheapest days of travel.
• As these are not AF-KL flights then does that greatly reduce the availability to me? It seems that not all the MU flights (2xLGW and 1xLHR each day to PVG) are available for FB Miles redemptions. I think there are a lot of restrictions when redeeming Miles on partners and it's not as great across airlines as the alliance would lead us to believe https://www.flyingblue.com/en/spend/flights/rewards (don't want to get distracted by that point).
• I cannot see the flights with the transfer (LGW-KIX via PVG), does this mean it is 0% ability to book connecting flights and it must be separate one-way tickets (LGW-PVG and PVG-KIX) with the usual problem that holds if a missed connection happens?

Of course, it'd be different (easier) if I was paying cash, e.g. can see them all in Google Flights, but I've got ~450k FB Miles and should start using them.

Thanks