You can definitely download Ubuntu 18.04 LTS and install it to replace your current installation. Considering that you've already "tried everything" - a reinstall is really the only option left when you've tried everything else. Thankfully it's very easy to do and Canonical has made a nice tutorial.
Ubuntu 16.04 LTS came out in April of 2016 and the first point release came out in July of that year. After the first point release, an upgrade is generally considered stable and the upgrade process to be clear of significant bugs. Ubuntu support for LTS releases follows a predictable support schedule for 5 years of community support from the release date.
This gives LTS users 3 full years after the next LTS has been released to upgrade to that release. The support window is actually so long, that before it expires, the next next LTS has already been released for a year, in this case 20.04.
If you would like an "extension" on your support for Ubuntu 16.04, you can sign up for Extended Security Maintenance (ESM). The basic level of support gives you access to updates for bug fixes and other security patches. This should be enough to help make the upgrade more successful. You can choose a paid option if you need much more help than that.
