Here are the commands:
The Actual item: /give @p minecraft:blaze_rod{custom_tag:1b, display:{Name:"[{\"text\":\"The Scorching Sizzler\",\"color\":\"blue\",\"italic\":false}]",Lore:["[{\"text\":\"Worker Grade Weapon\",\"color\":\"blue\",\"italic\":false}]","[{\"text\":\"(Unsellable)\",\"color\":\"dark_red\",\"italic\":false}]"]}, Enchantments:[{id:fire_aspect,lvl:10}], AttributeModifiers:[{Slot:"mainhand", AttributeName:"generic.max_health", Amount:-0.8, Operation:1, UUID:[I; -1, -1, -1, -1]}]} 1
This is the repeating command block: /execute if entity @a[nbt={SelectedItem:{id:"minecraft:blaze_rod", tag:{custom_tag:1b}}}] run effect give @a[nbt={SelectedItem:{id:"minecraft:blaze_rod", tag:{custom_tag:1b}}}] minecraft:fire_resistance 1 255 true
Again thank you so much!