Let me start by giving general answers and maybe ask some questions. I think the 101 tempo must be on the sheet music. Usually, before the tempo number there is a note value, like an 8th note or a quarter note, then, an equal sign (=), then the number. So if that is what you see, it’s telling you 8th note goes 101 bpm. I must say, it is unusual to request 101 bpm. Usually it is an even number, so maybe that was a typo. Don’t get too bogged down with tempo markings like that, though because it is a suggestion by the editor, not the composer. You will hear well known, well loved pieces played at a wide range of tempos, so you have some room to work in.
I would definitely need to see the music to answer the second question.
As for tenuto over one note, this is usually asking you to break the tempo by stretching that note slightly to give it emphasis. Of course, the interpretation must be taken in context of the musical line, so once I see that music, I can confirm or explain it more.