Lol Minato didn't have the time to write down a message. The village was in grave danger, he had seconds to move in order to protect it.
And Tobi couldn't get the Kyuubi from Naruto, he waited until Kushina was pregnant cause that was when the seal weakened, allowing him the oppurtunity to steal the Kyuubi.
Dude, Minato and Kushina were in a barrier made by kushina with Kurama inside, the village is fine now. And AFTER the frog left kushina had a long speech to Naruto they had plenty of time. And all tobi had to do was kidnap naruto anytime between age 1 and 12 (when the series starts) he would have plently of opportunites especially with Naruto being alone all the time. hold him hostage and malnourished untill he can extract the kyuubi just like the other tailed beasts. The only reason the literally hundreds of options obito had to take Naruto didn't happen is because of plot. That's bad writing 101.