If a company chooses to keep an employee they value, the do not cut his salary, unless you want them to be disgruntled as well. A slight raise was to be expected if the Spurs were gonna sign him. 4 years is a bit surprising though, as I would have expected 2 or 3 max.
Bonner is a hard worker, and he won't be expected to fill a big man role this year. Only to hustle on defense and hit 3 pointers. Rebounding and interior defense will fall to the other bigs...TD, Splitter, Blair, and Mcdyess, two of which I expect to be on the floor with Bonner at the same time, most times.
The Spurs ability to sign Splitter, and another player with the LLE is unaffected by this move.
Put your big boy pants on people and relax. The Spurs know what they are doing.
Believe.