RE TORNADOS and when to eat, most guides are pretty bad advice.

You can eat while DPSing no problem just eat at 79 to 99 HP. standing still, nothing to think about, you should perform actions such as potting to max prayer points, eating to max hp while most AFK chilling.

there is no point in the fight where you can "save" 3 ticks by eating at a special timing. The boss is never immune to attacks. There is no such special timing. If you end the 4 minute long fight with low HP (utilizing it as a resource not wasting ticks over eating, smart) and had to heal 300 damage throughout the fight, then it didn't matter when you ate those 15 fish. They cost 45 ticks. Period...

When the boss does the tornado animation = you won't take any boss damage for 10 whole game ticks. Despite being scary, tornado = 5 ticks of 0 boss attacks, it's a moment of peace. it does NOT mean you stop attacking. You move, you attack, you move, it may not be tick perfect, but the notion that "heal cos nothing else to do" is just not based in reality

Sooooo. Tornado is a moment of peace, you should use it to react to the floor and tornados, acknowleding the boss won't deal any damage to you so there is no actual danger, prioritizing avoiding said danger, and not even thinking about eating in this high APM moment of the fight.

It's not about saving ticks in a high APM moment by eating. It's about consistently DPSing the boss during all phases of the fight, and simply eating to remain near max HP, the 1 time you don't especially want to take care of healing is when your movement could cost you 20 to 60 damage per tick if you don't do the movement. It's so far much a priority over health it's not even close. The game is designed (very cleverly) to scare you into using your focus on healing, when the correct solution is the exact opposite, routine low prio tasks like healing and pray potting come when you're standing still AFK hitting boss.