8/15
As far as I know, Richie started at 5:07 and he claims that he played several hours because he kept leaving the stage and they kept calling him back but, I've got the entire concert either from sources I've collected over the past 20 years and the 38 CD release from a few years ago. That particular source is NOT the full concert, I've got a lot more of it than Andy Zak put into that collection.
If Richie played for nearly 3 hours, why is there only about 52:00 of his bit in that boxed set? Well, if I add in the bits I've got that Andy didn't include but, that's only 2 or 3 minutes. Also, if he played until nearly 8:00, how did the Swamii get on at 7:10? How did Sweetwater get on at 7:30?
The recording I sent you can vouch for Sweetwater going on AFTER the Swamii. During their set, one of the guys in the band says something like, "As the Swamii said, Kick out the jams.".
So far, before finding your schedule moments ago, the only thing I had to go on as far as scheduling was what's on Wiki. According to that, every artist (on day one) after Sweetwater overlaps into the previous artist! Wiki says Sweetwater plays for 40:00 starting at 7:30. However, I have 62:00 worth of their performance! That means, they played 2:00 into Bert Sommers' starting time at 8:30! Bert's part of the show runs almost 42:00 followed by almost 18:00 of announcements. That's a full hour. At least 10:00 into Tim Hardin's start time at 9:20. He plays for an hour and 6 and is followed by another 19:00 of announcements. Wiki says he only plays for 25:00!! Even if he DOES start at 9:20 and plays for 1:06:00, that means he plays at least 6:00 into Ravi's start time. And we STILL have that 19:00 of announcements BEFORE Ravi goes on! Ravi plays for over 50:00 and then there's about 7:00 of announcements pushing Melanie's start time back 17:00. She plays for 27:00 followed by 8:00 of announcements. Finally, we get a 25:00 break between her and Arlo. He plays for 46:00 and we get just over 1:00 of announcements and about a 3:00 break until Joan comes on.

8/16
I've been checking the rest of your timings and, at least on Sunday, there's one flaw that I've found, so far.
If Ten Years After DOES go on at 8:00, The Band can't possibly follow by 9:15 because there's over 16:00 of announcements that come after TYA. I have no idea if the turntable stage actually worked (I heard that the wheels under it collapsed as soon as they tried to use it) but, if that was working, The Band COULD'VE started at 9:30 but, there would've only been 53 seconds between the end of the announcements and the start of their set.
Another flaw, you've got Johnny Winter where B. S. & T. should go and vice versa.Chip Monck DOES make an announcement after The Band plays that there's been a sudden change in the line-up and that Johnny Winter is next.
Something else doesn't seem to mesh, here. In the movie, Paul Butterfield plays in broad daylight yet, the schedule says they went on at 4:30 a.m.!! I'm only about an 8 to 10 hour drive WSW of there and, this time of year, we don't get daylight `til 6:15!! Even at the peak of the summer solstice, daylight never shows up `til just before 5:30! And, if they start at 4:30 and it takes them 1:08:33 to play their set, not only are they still in the dark but, the announcement after it is only 19 seconds so, why does it take Sha Na Na a full 2 hours to get set up to play? How long does it take to set up microphones, a bass and drums and the electric piano that's been on stage for at least a day? And then after a half hour set, it takes Jimi another 2 hours to set up?

8/16
I just found another mistake on my part for the Sat. schedule! I played the pre-Country Joe announcements as if they were post-Quill and, at the end of them, Chip announces the start of Joe's set!! OOPS!! So, playing them that way means there's a 10:00 gap between Chip announcing him and him actually starting his set!

8/16
I was just checking out the Saturday schedule and it looks to me like some of the post-dusk timings are impossible. If Canned Heat goes on at 6:45, Mountain can't possibly go on by 8:00. Canned Heat plus the announcements after it total about 1:50:00. If they are using the turntable stage, I can see Mountain going on by maybe 8:45 but it'd probably be closer to 9:00. BUT, if they DO start at 9:00, that means The Grateful Dead can't start at 9:30! If GD goes on at the more likely 10:30, CCR can't possibly come on before 11:45. Then, there is more than an hour break between CCR and Janis!
ISB can't possibly start before 5:35

8/17
I just heard a Howard Smith (he was an on-scene reporter at the festival all 4 days) t.v. report where he said Janis played `til well after 3:00 a.m. so, Sly COULDN'T have started at 3:00! 3:30 is more possible but, I'm not even sure that could've happened, knowing how most bands tend to take FOREVER to tear down and set up!!

8/18
Just now heard about 1:00 after The Band finished, someone on stage says they've decided they're going to wait `til after Winter because somebody or something they need is not there yet to be able to play their set and, seconds later, Chip announces they've JUST had a change in the running order and Johnny Winter is going to be next! So, that confirms that he went on BEFORE B. S. & T..

8/21
There WAS a Howard Smith report right after the concert where, I'm pretty sure he said that Jimi finished up at 10:00 a.m.. I'll have to check that again. If that's correct, that means Jimi started before 8:00.
Interesting side note. A few days ago I discovered that one of the guys from Sha Na Na had a hit solo record in the mid to late `70's called, "Shannon". It was on Lifesong records, an ABC subsidiary. The song was about his dog, Shannon. After the concert was over, I have at least an hour's worth of chatter from the stage or audience and some woman says the name, Shannon, like it's a dog she's calling! I wonder if that was his dog! I know there was at least one other dog there! In some of the early Sunday chatter, which sounds, to me, like it's taking place in one of the medical tents they had set up, a dog named Lucy (I think) does a lot of barking for a few minutes! It sounds like it's INSIDE of some sort of building they put up because it sounds like there's a wooden floor! I suspect it's one of the medical tents because after a minute or two into the recording, you can hear some guy yell, "I wanna GO HOME!!", like, he'd had enough of this shit and doesn't wanna stay, anymore.

8/23
I just found something else that'd be very helpful! It looks like a much more accurate list of start times for the bands at Woodstock!! Here's that list.
https://www.rockfiles.co.uk/rockfiles_files/Woodstock.htm