@Roifield have you considered moving the site to a wordpress.com version? I had similar but less extensive problems with russian hackers on a site I used to run, and moved from wordpress hosted on my domain to a wordpress.com site and it solved the problems instantly as the software is always up to date. The downside is that you can’t use third party plugins, but there are quite a few standard ones to choose from.
There are various plans, the paid ones allow you to use your own domain name. There would be a one-off cost for someone to customise the CSS to the design you want, and an annual cost of hosting, but I reckon it’d be cheaper than what you’re currently paying. It’d be a trade off between functionality and hassle, but it sounds like you’re having heaps too much hassle with the current set up!