Sorry, I’m not a Rila (neighter English) expert,
D. 1: Just under (north) the Musala peak on the way to Musala hut is a cirque lake (30 min) with the Ledenoto ezero/ Everest shelter, where you can also ask for a bed. (By the way, the common way to Mussala is: Sofia – Borovets resort (70 km / 1 hour) – Yastrebets (20 min via lift) – Musala hut (1 h waking) – Musala peak (another 2-3 h, depending on the route).)
Two years ago I made your Day 4 (not from the hut Malyovitsa, but from the Hotel/ ЦПШ, which is 30 min. downhill.) We started 6:00 am (it was darrrrrk; today the sun rises about 7:00, but it’s light half an hour earlier) and were at Rila monastery at 15:00 pm (to catch a bus to Sofia by the way). I think there are hotels near the monastery.
But I was wondering about your Day 5. You are going back the same way as Day 4 and not the direct way, if you are planning to go again through Malyovitsa Peak. If you go uphill along the Dalgia rid to Mermer/ Mramoren vrah, you can turn directly left (west) on the ridge to the 7 Lakes.
Another mountain forum is http://planina.e-psylon.net. Unfortunately it isn’t working right now, but may be later you can ask there.