So Sa-Yan is alive and well, in this chapter it's been 30 years they've been together . When Ilic discovered the will he actually got pissed of about the content and also because he has some regrets from the period when Sa-Yan was really sick like 10 years prior to this timeline. [I won't spoil the reason has it's the main point of next chapter] (But basically most of what was shown in the dream was real except the death of Sa-Yan of course and the pig stuff but wait for next chap for this it's funny).
About Sacha, first time she appears, she's the only daugter of Leisa and the Empress. It was only mentionned in previous chapters that they already had 3 kids.
They old lady is called Mel I think, anyway she's just a servant here to take care of the princess. About why they are here : Ilic used them has an excuse to escape the palace.
I hope this cleared most of your questions, well most of them are answered in the next chapter which seems to be the last.
Yep post sickness it’s been 20 years. Basically he was sick and wrote the will in the chapter you saw. Then I guess he got better, don’t know how. Then time skip 20 years happens, everybody is now old. Suddenly, iliac has a nightmare about sayan dying to scare the shit out of readers lol but they are alive and old/grand uncles to the little girl

sa-yan was dying kinda idk maybe? it was confirmed he was sick then he wrote a will saying after his death illac gets to be free and his enemies will be destroyed after illac saw that will he had a dream where sa-yan died frfr and i guess he was so stressed from reading that will that he had that dream but he wakes up sa-yan is fine and then sasha? i think forgot she existed cause i fr thought did sa-yan had a kid before he died? also who's that old lady with them anyhow very confusing read