Likewise, I once wanted to make my own, healthy, sugar free, organic mix. I started trying to work one out and the ingredients were going to be massively expensive to make enough for 6 months. So I bought a good organic, sugar free mix instead

Which had just come out at the time.
The other main issue with a home made mix is - even if you get everything right (and there have been some sad stories where people didn't) it won't include the fortified vitamins that a commercial mix includes and supplementing vitamins isn't an easy thing to do (and you could give too much or too little again).
Working out the protein in particular is incredibly hard. Plus the percentage of fats and roughage etc, It's a great idea and I think a lot of people like the idea, but hamsters have such fast metabolism that it's fairly critical to get the balance and content right.
These days people consider a muesli mix is much better as it encourages the natural foraging instinct and it's nicer for hamsters - yes they may not eat all of it or eat some bits more than others, but hamsters do have an instinct so they only eat what they need and I have never had one with any nutritional issues despite leaving the odd thing. You actually never know which bits they eat as they tend to eat from their hoard

. Most of what they take from the bowl, they hoard and then eat as and when from the hoard.
I use the Bunny Dream dwarf expert mix - it is very very good - it even smells nice unlike most pet foods! The trouble is most of the good mixes are German (including the Little One although at least that's available in Uk pet shops). And are only available online. But I like the Bunny Dream one a lot so I just put up with ordering it online and get it from Vetsend. A bag lasts a long time but I get two at a time to save on postage.
Bunny Nature Dwarf Hamster Dream Expert is formulated specifically to correspond to the nutritional needs of dwarf hamsters. Shop online here!
www.vetsend.co.uk
It contains mealworms. Like the Little One, it is a bit low in protein at about 15%. This is fine once they are a year old but during their first year the protein needs supplementing a bit - but you're already doing that with giving some egg and bits of chicken etc. (A nut once or twice a week goes down well as well - half a half walnut is appreciated as a treat!). I tend to use plain cashew nuts (which you can split in half for a dwarf hamster) and walnuts. They are protein supplements too.
I haven't tried the Little One Mix but it sounds good and has good ingredients too - if it's more easily available. But I'm happy with the Bunny Dwarf one. Which has mealworms in as well and the right sized pieces and seeds for a dwarf hamster.
Back to Pumpkin seeds as treats - that is fine - I also use healthy treats rather than sugary ones, and pumpkin seeds are a good option. I wouldn't worry about how many to give - they will only eat what they want and hoard the rest. Eg with a bit of walnut - I often find them put in a special place and just nibbled at occasionally. Sunflower seeds are good for treats and taming treats too but maybe not too many of those as they can be a bit fattening if they have too many. But they'd need to eat quite a lot for that to happen! So a few a week is fine too
Not sure if anyone has mentioned freezing the food for a week first?