A couple questions about how to do these all to do with procedures

Q1: 
a. give health boost or absorpsion effect and set the level to be equal to "get max health" - "get current health" (minus block found in logic section) 
b. If you need help with when damaged while having enchantment then here: "Event Trigger" set to "Entity Attacked". put an if block (flow control) and set to "has 'Provided Itemstack' enchantment [your enchantment]" and set the do section to part a.

Q2:
a. in the entity's triggers section, there should be a "when struck by lightning" trigger. add a procedure to that.
b. make it so the event/target entity despawns and spawn a new entity at that location.

Q3:
a. create 2 local variables (right side of procedure interface) name them "potionlevel" and "potiontime" and set them to number
b. place a set variable block under the name "potiontime" to the amount of ticks left in the potion effect
c. place a set variable block under the name "potionlevel" to the level of potion effect
d. make it so when a certain action is achieved through an if block, place if blocks inside it and make it so that if you have a certain potion effect, itll give take away that effect and give you a different one (ex. remove poison and add regeneration)
e. set the level of the potion to "get local: 'potionlevel'"
f. set the "for __ ticks" section to "get local: 'potiontime'"
 

god that took a while to write

btw cool trick: tinker with all the elements before creating an actual mod so you at least kind of know what you're doing

Make a procedure that has the trigger, something like entity takes damage. Check if the person who dealt damage is the player, and if so, give the player health boost effect with the level amount, find this is custom dependencies.