I think I am half way between these many replies. I generally don't check a bag, but that's mainly because I'm usually doing some amount of public transport at the other end and I just don't want to faff with that.
My answer is to be super organised with my backpack and to make sure my carry-on suitcase won't need opening at the airport.
So that means splitting out liquids and hair straighteners etc as you have.
Clothing wise, if it fits in the suitcase I'm not that bothered by how much it weighs. My solution to finding it hard to heft about/lift over my head has actually been to do some weight lifting at the gym. I can now happily carry two carry ons up and down stairs, put them up in the lockers etc. If you can manage to get a carry on suitcase weight above 10kg that will be impressive, so it's unlikely it will weigh more than that. That's a personal preference though because although I'm a "light packer" (have done 2.5 weeks on Ryanair hand luggage), what I actually am is a super efficient and dense packer. If I am going somewhere warm, I generally take 2x nighties, 1x thin dressing gown, 4-5x dresses, 1x leggings, 1x denim jacket, 1x thin long sleeve top for under dresses, 1x shorts, 2x t shirts, pants, socks, 1-2x swimsuit, goggles, spare glasses, low top converse, sandals, plus charging plugs. That's in the suitcase.
And then I take a rucksack which contains:
Battery pack, kindle, phone, IDs etc, water bottle, jumper, liquids, any airport snacks, an umbrella if I want one, hair brush, electric toothbrush (reduces the risk of my case getting pulled if everything electronic is in here). Anything that needs pulling out for security goes in a thin sub bag. My phone and IDs go in a small cross body which can also go into the rucksack for boarding but no one has yet questioned it not being there.
So to me the amount of stuff you took looks about normal - though I find you need almost as much for 4 nights as a week and you'd probably have felt it was fairly good packing I'd you had gone for a week. And just probably need a rucksack or similar so you aren't hefting a weighty tote around.