You sure are fortunate to have a doctor who checked it. More are, but it amazing how many still don't.
I hope the doc specified that you take at least 1000 mcg B12.
I hope also that the vitamins get you down into the lower half of normal for homocysteine. That is desireable.
I don't know about the gums specifically, but I do know that low B12 can cause abnormal bleeding. Of course other things can too, even failure to floss.
I hope you will get copies of all test results. No one will be willing to spend the time exploring patterns, etc., that you will. And it is surprising how many docs fail to give important information to patients, and amazing to me that some even falsely represent the results.
I would pay special attention to nutrients, in addition to paying close attention to what the doc finds. It does sound like you have a nutrient deficiency, whatever else may or may not be going on.
rose