A few thoughts -- and I still have lots to learn myself (i.e., this might be the blind leading the blind)!!!
1) Having a nice 5 hour or so ride in there is good,
2) For Tuesday, you can do five 5-minute intervals to add some variety should you get bored of the 20min intervals.
3) For Wednesday, I question technically that you will be able to 60min at ftp. I interpret ftp as the absolute best you could do in "stp" like conditions for an hour. Theoretically, it can be achieved, but, practically, I don't think one can make it. Nevertheless, you can try to hit it "in spirit." I have a feeling that will be a tough workout after the Tuesday workout. But, if you do it, good for you.
4) I don't see any training above ftp? You might want to think about that as I believe it could help raise your ftp, which, in turn, could help your performance.
Given your purpose and that you are new to this, you might consider being flexible and looking to learn and adapt as you go along. A plan is great, no doubt!! But, personally, when trying something new, I tend to look for opportunities to experiment and learn.
In the end, it sounds reasonable. I sense that you feel your base conditioning is fine. If not, consider throwing in another longish ride during the week,
If you have a trainer, seriously consider using it and raising your front wheel to simulate whatever grade you like, and then crank away.