The convention I was taught is that "This... and that" is quoting someone who pauses after 'This', while "This [...] and that" indicates that I elided something. This seems to me both useful and clear.

Also, I'd try to avoid ellipses in a quote unless you are in fact leaving something out. I suspect here you just meant it to reflect the doctor's speech pattern, but it's a bit confusing.

"Word... Word" has a different meaning to "Word ... word". The usage in this comment would not confuse many and replacing the ellipsis with a period would change the meaning of the quote. As it happens most sources I can find don't include the ellipsis so the addition would be a mistake. So I agree with you in this instance and agree in general with a slight modification to "adding ellipses to a quote".