Spacing and dot weight in bsmallmatrix (from mathtools)

MWE

\documentclass{article}\usepackage{mathtools}\begin{document}Le signe $(-1)^{i+j}$ suit un motif en damier :\(\begin{bsmallmatrix}+& - & +& - & \cdots \\- & +& - & +& \cdots \\+& - & +& - & \cdots \\- & +& - & +& \cdots \\\vdots & \vdots & \vdots & \vdots & \ddots\end{bsmallmatrix}\)\end{document}

Questions

1. There appears to be some horizontal empty space around the matrix.How can I remove or reduce it?

2. It seems that \cdots is not as bold as \vdots and \ddots.Is this actually the case?If so, is there a way to make the various dots visually consistent?

THANKS A LOT!