Alright, let's do this
Keep in mind that since Pain had full intel on Tobi's techniques, after working with him for so long and watching him along with Konan. So obviously, he'd be wary of Tobi's techniques, since he knows that his favorite thing to do in battle is to absorb the enemy into his dimension. Due to this, and due to the fact that Pain knows that Tobi knows the weakness of the paths, he'll obviously use a battle formation according to that, most likely something like this:
To be able to use the shared vision to it's fullest, so Tobi won't be able to appear out of nowhere and surprise Pain. Keep in mind that Tobi doesn't appear instantly, it takes time for him to appear, although of course it isn't to long. However, it should without a doubt be enough to utilize a Shinra Tensei to keep the rest of the paths safe.
Anyways, Imma take a look at your points.
1. This technique is useless against someone with a Shinra Tensei. Tobi could use this either for
1. Defending himself, which would without a doubt just ending in Pain using Bansho Tenin to pull Tobi in the direction of the wall, forcing Tobi to hide himself in the dimension or burn.
2. Trapping the paths, which would end up with the Deva using Shinra Tensei to simply blow the wall away.
This technique is close to being useless in this fight.
2. Izanagi is pretty much just like an extra life in a video game. If he gets hit by a technique, he can come back in the same shape as he was in before, and then it's done. However, he won't be able to "surprise" Pain, as you say, due to his sensory abilities. The second that Obito appears, Pain will know. There's also the fact that the users body fades away before appearing again, which would without a doubt make Nagato stay alert, since he'd know that something wen't wrong.
3. The Wood Release techniques are powerful, no doubt, but the fact is that the techniques Obito has shown are nothing too large for Deva and Asura Path to handle. Heck, look at these pages here.
The Wood Release technique's Obito has shown so far are not strong enough to hold up against something as strong as that.
The close range techniques Obito has shown will not be a problem either, as he needs to solidify himself if he plans on doing actual damage to Pain, meaning that a Shinra Tensei would be an effective counter.
4. Please, close range attacks are not exactly recommended when going up against someone like Pain.
KO ? Ever heard of Deva Path and Preta Path ? This is just a simple Fire attack, the only difference is that it's spinning..
6. This is essentially just the same thing as nr. 3.
Pain has been shown to have excellent reflexes (look again at the page where Kakashi tries to surprise him) and this would be countered, like most of Tobi's attacks, with a Shinra Tensei.
I don't really see how being a sensor has anything to do with this, and I'm not sure that I even agree with Naruto being the best one. He wasn't even in SM at the time.
7. It's not "long range Kamui" he's simply warping himself someplace, and warping himself back. It's the same old Kamui, he doesn't have one similar to Kakashi.
Let me try to break this down one more time.
Pain has knowledge
on Kamui. He knows it's weaknesses, the fact that Tobi needs to solidify when he's warping something other than himself, and the fact that he can't withhold it for more than 5 minutes at a time. Knowing this, he'd obviously be careful not to let Obito warp one path at a time, by forming a circle and using the shared vision to make sure Tobi can't surprise him. The fact that Obito needs to solidify when absorbing one path means that he'll be vulnerable to the attacks of the 5 other paths when warping one of them. His fire-techniques are countered by Preta and Shinra Tensei, and his weapons are countered by Shinra Tensei and the Asura Path. He has no way whatsoever to get to Pain, due to Pain knowing which actions to take when facing Tobi. The paths may have their weaknesses when separate, but since Pain has full intel on Tobi, he won't be dumb enough to actually split them up, no, he'd make them stay together and use the strength of each one to protect the others, with the Deva Path being the main factor.
The last part of your post is simply outrageous, since this is the largest tech we've seen him do by far
, and that was when he was in an emotional rage with the spiral Zetsu helping him and boosting his moves.
Pain has this fight.