I have been a student of JSA for 22 years. The vast majority of my practice is still done with a simple bokken. For iai kata, a Japanese-made iaito from alloy is more than sufficient. For tameshigiri, there are also tons of good options, none of which involve using an antique. In those 2 decades, I have met many hundreds of other students of the sword. NONE -- not a single student, regardless of skill -- would contemplate using an antique sword of this caliber for any kind of training. The oldest blade I've seen used in JSA context were some WW2-era showato and gendaito, and even that very, very rarely.
Antique nihonto are finite in supply. There are no more being made. Arguably, they are getting fewer in number every year due to amateur "polishing," poor preservation techniques, neglect, theft, abuse, etc. Please heed the well-intended advice and feedback you're getting and not use an antique for training. It's just unnecessary and not a good way to preserve these irreplaceable works of art.