I am sorry to hear that you're not satisfied with service. In many cases, 20GB is enough data for normal use, however, streaming videos online eats a large chunk of data. If you are trying to stream a lot of movies and TV shows, you will want to set the resolution as low as humanly possible so that you can view more content. Satellite Internet in it self, isn't a replacement for TV and DVD/Bluray rentals. If you use Youtube and similar services, make sure to enable Video Data Saver, and that you set your players to Automatic for resolution. Alternatively, you can disable Video Data Saver, and manually set each of your streaming services to a lower definition to help conserve your data allowance.
For instance, Netflix typically uses the following amounts of data
Low Definition - 300MB/hour
Medium - 700MB/hour
High Quality - 3GB/hour for HD, upto 7GB/hour for Ultra HD (2k and higher resolution)
If needed, and you do run out of data, you can buy more, it's $3 for 1GB worth.
As for your desktop, if it's located a fairly long distance from your HT2000w, you will need to either connect to the HT2000w over wifi using a Wireless NIC, or run your own network cable from the computer to your modem. It is not the responsibility of the ISP to perform home networking beyond a few devices that are either wireless, or in the immediate area of your modem.
Just like Satellite TV, when it rains, yes, your service may go out, there's no way around this.