The Beta 2 Microglobulin is alarming only if it is elevated. I don't know of a cause for concern with a low B2M - many labs just say nl is <2.7 (or in your case <1.8).
I imagine the thyroid ultrasound showed "heterogeneous changes possibly related to multinodular goiter" but no large nodule. The anti-TPO is the most important test you mention as it means the thyroid is being attacked by the immune system - this causes changes seen on ultrasound (inflammatory changes). The TSH is currently normal suggesting the thyrioid is "hanging in there" pretty well - but the probability of progression to under-activity is at least 5%/year.
In the absence of symptoms, I would not necessarily treat. A low dose of synthroid to bring the TSH to around 1 would be reasonable if you have fatigue or other thyroid symptoms.