first two problems are on my head. Issue here is that use small hack to force using different then system language. Anyway this information is not available to other add-ons and also when locus needs some information from system (like name of add-on function ), this information is not send to system. Because using other then system language is generally not support ( bad idea ), I see no simple solution here.
Similar it is in second problem. This about add-on like about separate application, that just looks like small dialog. And this application does not know that Locus has some settings like "always screen on". And because when add-on is visible, Locus is not active app, this settings does not work for that moment.
Third is a question on @arcao.
Not sure if it's needed to search for some solutions of these two issues. I think that both are quire rare or not so serious. What you think.