I would recommend trying to up the resistance every few weeks, maybe not in 75 minute marathons but in smaller sets, just to help build muscle in addition to the cardio benefits

That's part of my plan.

Also I think the mechanical rowing machine you got might limit your range of movement?

It's a cheapie machine and for what it is - it's okay. I'm thinking of buying a Concept2. It's the gold standard for rowing machines and you can compare yourself to others easily.

i row 100x better while stoned with some energizing music playing. Fast beats in the manner that pleases you best, I've been enjoying the hiphop

So far I'm more of a rowing as struggle guy. It's just me and the machine.