The plugin part is somewhat irrelevant… The real question is where you can change the settings so it will automatically switch to mobile view at a higher width that what you currently have it set?
To further discuss the plugins, however, both of the plugins (sidebar and adsense) are very helpful - as many (most?) forums need to generate revenue and have other meta data and with the footer not being as good of an option with all the infinite scrolling, etc. - so these would need to work. And they quite simply do not without a more responsive design overall or having tablets get the mobile viewport.
For the adsense plugin it will only show the “mobile” ad size when in mobile view which means that it trys to shows a large banner ad on a tablet which doesn’t work and the sidebar plugin makes everything squish together more instead of just switching to mobile which would address problem as well by dropping the bar entirely.