Hinata would probably be extremely shy at first. She might blush furiously and be at a loss for words. After all, she has had a crush on Naruto for a long time, so it would be a dream come true for her.
One scenario could be when some villagers start to be mean to Naruto. Iruka steps in and scolds them, telling them Naruto is just a kid. Another could be during a training exercise that gets a bit too dangerous for Naruto, and Iruka quickly intervenes.
It also improves Naruto's skills a great deal. He becomes better at combat and using his ninja techniques. For example, his Rasengan might be more powerful or more easily controllable after Iruka's training. Moreover, Naruto's confidence grows under Iruka's guidance. He no longer doubts himself as much and is more willing to take on challenges.
If he asks Hinata, she would probably be overjoyed. She has always been in love with Naruto, so her answer would most likely be an immediate 'yes' with tears of happiness in her eyes.
Physically, Iruka takes care of Naruto's symptoms. If Naruto has a cough, Iruka might make him herbal tea to soothe his throat. If Naruto has a fever, he uses cold compresses to bring the temperature down. He monitors Naruto's condition closely and adjusts his care accordingly, making sure Naruto is on the road to recovery as quickly as possible.
At first, it might start with Iruka showing simple kindness to Naruto, like making sure he has enough to eat. As time goes on, Naruto starts to see Iruka as a father figure. He looks up to Iruka and wants to make him proud.
Well, in the fanfiction, Iruka may be protective by constantly checking on Naruto's well - being. He could ensure Naruto has enough to eat, is getting proper training, and is not being bullied by other villagers. He might also be protective in the sense that he gives Naruto extra attention and guidance in his ninja training, more so than he would for other students.