1. do they need both cuttlebone and a mineral block, and should i just buy both?
You can provide them as they can provide a chewable device, however on a healthy diet, they aren't necessarily required.
2. do they like to have shreddable toys?
Each birds personality differs, so it's hard to say. Some may prefer shreddable toys, some may enjoy toys that make noise, some may enjoy shiny toys, some may enjoy foraging toys, etc. Provide a variety!
3. is 5 perches and a swing enough? (of course rotating, keeping swing in, just swapping perches)
As long as you make sure that the perches are of different sizes and textures, then yes that should be sufficient.
4.is a 23.5 x 15 x 23.5 cage with 1/2 wiring big enough for a parrotlet?
It's not a bad sized cage, although if you could, look for larger alternatives.
5. is this a quality food? (ingredients below, i will be adding fruits, veggies etc daily)
In and of itself, no. With added fruits (no more than 10%), vegetables, sprouted seeds, grains and legumes, then yes, it may be just fine!
4-I will look for a larger sized cage, but its what i can afford and I'll be playing with him out of his cage.
5- I will add fruits veggies and seeds