Wow, you’re really doing your best to care for your bun in the best way. How great to see that you’re such a responsible bunny owner ^_^ You’ll have such a great time with your bun, he’ll reward you many times over!
It looks like his diet is already chock-full of healthy foods and snacks. Rabbits get enough vitamins and minerals from hay and pellets, and the fruit and veg are a nice addition in case anything was missing.
As a rule you don’t want to feed your rabbit too many minerals, because their urine is different from other mammals. Theirs is highly concentrated to dump excess minerals, and rabbits who get too much calcium or oxalates in their food develop painful kidney or bladder problems.
Just like in humans, the idea of multivitamins sounds wonderful, but they may do more harm than good. A normal diet should be more than enough to get your vitamins and minerals, and only in case of deficiencies supplementation is neccessary. More isn’t better, it’s really the other way around. Some vitamins and minerals are actually bad for your health when their daily intake is too high. For some vitamins that dangerous dosage is only 3-4 times the amount of the recommended daily amount. Vitamin A is one of these potentially dangerous ones, and here in NL there are more and more people who have health problems from vitamin B6 supplements.
So for both humans and buns: more isn’t better, it can even be dangerous. Only supplement in agreement with a doctor or a vet, and only when really neccessary, for instance if you have a diet which is lacking, or if you have malabsorption problems.