Yep, BTU port is set to 100Mbps even though it's capable of 1Gbps so your internet is limited to 100Mbps. A few of us here has faced that problem. TM can reconfigure the BTU remotely but more likely, they'll just change the BTU.

I suggest a Mikrotik RB4011iGS+5HacQ2HnD-IN. The product model alone makes it sound so impressive.

Cool, new kind of radio waves?

Look at the model and its specifications. This will tell you if it's theoretically capable of 1Gbps. This applies to both the BTU and the card.

Once you know that, you can test. Of course, when you test, you don't test 2 unknowns. So you need to test against a 3rd network port that is known to work at 1Gbps.

If you don't have that then you'll have to start making assumptions and work from there.

Of course, before all that, you need to ensure that your test equipment, eg: your network cable, will not influence the test.