Family Budget - where are we going wrong? Is it me?!

Hi good people, really needing some collective eyes and brains across our family budget, to get an idea of why we just can't make it work. My worry is that .... I am the problem. Or, is it that we are unrealistic about how much we can save?

The people: Me: 43 on $169k per year. Husband: 45 on approx $600 a fortnight (part time, variable income as he's a hairdresser). 2 x kids - 7yo and 3yo. We also have 250 per fortnight from my MIL who lives in a flat downstairs. We live in Wellington and our rates are insane.

The situation: despite setting up what I thought was a great system of having a sinking fund that is for all those expenses like extra-curricular fees for kids, WOFs, my gym membership, and other accounts for emergency funds and travel, we are ALWAYS dipping into them!! We never seem to be able to build a safety net, despite me earning what I am sure is considered very good money. I feel like an entitled idiot. How are we not making it work?

We've tried and tried to get our grocery expenses down as I know $1000 a fortnight is insane, but with 2 x pets, nappies etc (almost phased out thankfully), crazy quantities of 'milky', etc etc, it just feels impossible and we really like fresh, healthy food, which seems like it's at a premium at the moment.

I have managed, by digging my nails in and just fucking doing it, to invest around $3500 with our Milford Assets mirror account. But that's been hard, and things keep cropping up. We are also planning a very short trip to Queenstown this year for my husbands birthday, and we are going to Fiji for 11 days in August as we've not been anywhere as a family. At the moment a lot of our savings focus is on Q town and Fiji. But, according to my spreadsheet we should be able to do those things AND put some money aside for savings.

What's the problem here? I'm worried it's me .... but it also feels as if there's eternally something massive to pay for that I haven't factored in, and if our budget was working properly there should be money in our sinking fund to cover these things .... but there's not. We use it all. We don't even have life insurance, which I know is insane.

Here's our budget. Please be kind!! I was not raised in a money literate family, and I am sincerely trying my best to get my family sorted. It's also quite hard being the main breadwinner and trying to manage all the finances and balance fun and living with being careful.

https://docs.google.com/spreadsheets/d/1EAmBL6M8aT5FpGeL1W34PBt57seTQ2J7/edit?usp=sharing&ouid=101454021905106717050&rtpof=true&sd=true