Tobirama was killed by twenty Kumogakure master bounty hunters; I'm sure that any person wouldn't live long in the same situation. The Iwagakure ninja Minato defeated, this could have been done by many other ninja beside just him; they were not that high-ranking of ninjas. Now, if Minato were facing 50 Kumogakure master bounty hunters, do you think he would defeat them all? And he did not defeat them all by himself - he had other ninja throwing kunai at the enemy to distract them so Minato could defeat them, so yes, he did have assistance. Next, even if Minato did receive information that there were a thousand enemy ninja on the front line, that doesn't mean he singlehandedly killed them all. You cannot use his words like that to fit your argument.
You say that everything you know about the Third Hokage is just from conversations that people had? If you recall, he fought Orochimaru during Sunagakure's invasion of Konoha, who also summoned Hashirama and Tobirama to take care of him. Is this not a battle where Sarutobi was forced to use all his strength? Incorrect facts again from you. If Minato were to go up against the same opponents, the results would be worse. For one, Minato doesn't know as many techniques as Sarutobi does, and secondly, if he tries defeating Orochimaru with speed, remember that there are two revived corpses, the two most powerful Hokages in history, that he must deal with.
During Madara's battle with Hashirama, Madara's objective was to take revenge against Konoha, so eventually he would have to make an attack (as shown in the manga), and as Fu and Torune said, counterattack makes him susceptible to defeat, in one sense or another. Once again, you are simply assuming that Madara did not have his space-time ability then; what is to suggest that he didn't? Provide evidence of your claim, otherwise it holds no ground. The Eternal Mangekyou Sharingan does not make one invincible, unable to be harmed; your observation that he got hit a considerable amount with the doujutsu should be obvious. Once again, nothing in the manga suggests that the Eternal Mangekyou Sharingan makes the user impervious to harm, so users, naturally, are going to be physically hurt. Despite the extraordinary speed Madara has, he is not going to be able to use it in all occasions, so of course we are not going to see it every time Madara is shown in the manga. And Madara's face is not "messed up" in the link you provided; he is simply roaring while battling a tough opponent. And in the last link you showed, Madara was, of course, making attacks to try and defeat Hashirama, so while Madara made himself corporeal, Hashirama could have stabbed him in that moment, thus defeating him. Just because he was impaled does not mean that Madara did not have his space-time ninjutsu back then; when two opponents battle, they will physical contact, in one form or another. But it does not mean what you are trying to say in your post. That is just another assumption.