does not want to stay where I want it to

Mac o/s Yosemite 10.10.4
Inkscape .91

Please attach the test case from the screencast (the Inkscape SVG file, with the original object and the pasted copy) to the bug report to allow further investigation of the reported problem.

Based on the screencast, the pasted object is likely pasted as bitmap copy (see solid white background as bug as the original object's bounding box). Please adjust the X11/XQuartz preferences for the Pasteboard as shown in the screenshot on the download page:
https://inkscape.org/en/download/mac-os/
then try again to copy the _original_ shape, and paste it in place.

The underlying issue for this (which also triggers the failure to actually paste in place) is already tracked in bug #307005.

Re snapping (second part of the screencast): snapping can be temporarily disabled by pressing 'Shift' while dragging the object with the mouse, or altogether by toggling off the top-most button on the snap controls bar.
Further details about whether or not the observed snapping behavior is to be expected or not can only be provided with additional information (e.g. the actual Inkscape SVG file as mentioned earlier). A screencast only shares a limited amount of information.

Correction (typo):
- as bug as the original object's bounding box
+ as big as the original object's bounding box

Re#3
- Please adjust the X11/XQuartz preference
Thank you for the tip
Done

Based on available information, linking as duplicate to bug #307005 (tracks underlying issue with XQuartz's default preference settings for the pasteboard).