You should definitely try going for the 100% ATK/-100% Resistance Wind buff, with a team like Iruka, Guy, Lee. Using the Wind main's 3 clones + Clone generator standard.

Additionally you should try to interrupt both casts of the bubble jutsu from the frog on the second round of it spawning with GUY and IRUKA.

Unfortunately 70 specifically happens to be a "Damage Check" of sorts. Interrupting the bubble attack on round 2 of the Summon fight can buy you an extra round usually, but the best tip is to increase your power and give it a few tries a day.

I usually spend about 10-15 mins every day trying to advance in Ninja exams (sometimes longer) as a lot of the fights have tons of randomness in them, and it does not get any easier past 70 unfortunately. It gets to the point of being silly and the only way of advancing being Chaosing enemies and hoping they kill each other before you die. The recommended power is usually a good indication of when you should be able to minimize the RNG and bruteforce your way through it exam.

I used Tobi, Iruka and Naruto 3* to clear 70, although I'm Fire and can disable Jiraya indefinitely using my sleep - not taking any damage in phase 1.