@fulmar
During your first twenty days of service your monthly data allotment is continually refilled by HughesNet. They do this as a courtesy, in case you need to update or upgrade your devices to current, so that it doesn't affect your normal monthly allotment. After those initial twenty days the data usage starts being deducted from the monthly allotment in the normal fashion. This is very likely why your data lasted the entire month last month, while this month you're running out.
Regarding the Wally, I'm not familiar with one, but if it has an ethernet port you can connect it to the HughesNet HT2000W modem using an ethernet cable. This way there is no need to connect it via WiFi. If an ethernet cable isn't a feasible method due to distance or the cable just being in the way and/or unsightly, you'll have to get the WiFi adapter for the Wally and connect it via WiFi instead.
You can certainly use the other WiFi source you have that available to you. In fact, if that other source is unlimited, and it works well enough, you may even want to consider using that source for your data heavy activities, such as streaming, as streaming can use a lot of data. In fact, if you do a lot of streaming with the Wally you may want to reconsider getting that WiFi adapter so that you can use the alternate WiFi source for the Wally instead of HughesNet. I say this because, as mentioned, streaming is a data heavy activity, and it won't take long to burn through 20GB doing so.
With this said, two WiFi sources can interfere with each other. If this happens there are likely certain adjustments that can be made to help mitigate the negative effects.
