Long distance caring will destroy you, as you're discovering. But you have a big advantage having someone coming in daily who's accepted by your mother. My Mum would barely let
me in half the time!
'Fortunately' I didn't have a family or relationship to worry about, so I started off going up to Mum on my days off, then I had to cut back my days at work, dropping back to just two days' work a week over the space of a year or so. But even that became unreliable as she'd panic when I was leaving, and I hate nothing more than letting people down. I was letting work down, and my Mum, so... So two days became one, then I took a year off, which suited work because they were trying to dump hours. And at the end of that year I decided I couldn't put Mum in a home 'so soon' when she might live another ten years or more based on her doctor's opinion of her overall health.
The dementia decline is relentless and inevitable, so now is the time to think ahead and either prepare for your mother going in to a home sooner rather than later, or to work out how you'll spend more time with her to ease your stress somewhat (being there is tough, but less tough than not being IMO!) Carers can come in multiple times a day, but unless you're very lucky, they don't remove the risks and stress significantly, especially when you're not able to easily check things yourself.
However I'll say that I was able to postpone my slide into life as a carer by installing a laptop and large screen in my mother's house (with the leads all taped together firmly and the power supply tucked away so she couldn't get to it easily to turn it off). Skype can be setup to accept incoming calls automatically, so I was able to connect to Mum any time we both needed it.
Of course it ended up with me working all night then leaving Skype most of the day while I tried to sleep, so it wasn't ideal. But for that period it helped Mum feel supported and reassured (sometimes!), and I was saving as much money as I could while simultaneously subsidising Richard Branson's next island purchase via Virgin Rail.
By then Mum was struggling to use the phone properly though, and often putting it down the wrong way, or not at all. So I'd have been stuffed if the laptop hadn't been in place. However internet issues and remote tech support can be a nightmare. That's helped in your case by the visitor you can work with from afar to tackle problems. I'd have sold my soul to have someone similar, but my mother was always a private person who hated visitors and that didn't improve with dementia.
I also put a couple of webcams in Mum's kitchen and the hall so I could keep an eye on her. So I was often able to head off potential issues in advance... though only by starting to live like some kind of security guard watching a prisoner. It didn't make me feel great, but it did allow me to keep a double life running for a while. But it was the hardest thing I've ever had to do and if I was starting again I'd have chosen a definite solution sooner (either going up there or institutionalising Mum). I'd probably have a few less wrinkles and a bit more hair if I had!
Sorry, this all turned a bit 'me, me, me', but hopefully my experience of the long distance slog is semi-useful. Not as useful as me going to bed though! Hadn't realised it was so late. I'd go through this again and try to make it a bit more positive if it was earlier, but it's not, and it's honest, so... good luck, and sorry if this is all a bit depressing. But if it helps, I feel like this whole process had made me a better person. A totally knackered, rather nervous about the future person, but better all the same.
And long-winded. Sorry.