1. The point of the barrier is to alert Jiraiya where Bee is coming from and prevent an attack from a blind spot. The barrier is huge so Jiraiya will be alerted the moment Bee crosses the barrier, long before Bee reaches Jiraiya so he will have plenty of time to react. Not to mention, Jiraiya has frog kata (though not to the extent that Naruto has shown.) Look in my sig. To top it all off, Jiraiya has two perfect sages perched on his shoulders so sensing Bee is definitely not an issue.
2. Did you seriously just say Jiraiya can't make multiple kage bunshins...Chapter 1 Naruto could make dozens of clones effortlessly, and Jiraiya admonished him during training for his poor chakra control. Jiraiya has huge chakra reserves, and the fact that he can use Sage Mode at all is a testament to that.
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. When he's in Sage Mode he has access to all that nature energy so there's no doubt that he can do so.
3. Hachibi's mass is irrelevant here. The swamp is just too huge. 30% drugged Jiraiya was capable of sinking one of Orochimaru's boss snakes with that swamp, and on the next page he critiques his own work.
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So even a healthy base Jiraiya can make a much bigger swamp than the one shown. Add in the Sage Mode factor, which enhances all ninjutsu by a lot, and the swamp would easily encompass the Hachibi without difficulty. Bee would be paralyzed by frog call, so whirlwind is not an option and neither is protecting himself from Bunta with his tails. To use raiton, Bee would have to go into base or V1, which would leave him vulnerable to Jiraiya's attacks - but it doesn't matter anyway since he'd still be paralyzed by Frog Call, so he can't stick a raiton sword in the ground (I have my doubts about raiton working anyway...)
