(i) There are some free online metronomes that are, in fact, adjustable to any beat rate you should desire within a particular range.
(ii) There is nothing at all wrong with practicing something (whether long or a short passage) at a slower tempo than any given recording of it. In fact, if you can't accomplish something at speed, the only option you have is to slow it down, and speed it up as you progress.
(iii) There is likewise nothing wrong with performing a tune at some slower or faster tempo than the "original" version of it. This is an aspect of expressing yourself, of course.
(iv) 72 vs. 73 BPM is not something I think is particularly noticeable. There's a difference of something like 1/100th of a beat per second.
