Astable 555 frequency problem
You should have a bypass capacitor across the supply terminals, close to the TLC555. Something like 10uF electrolytic in parallel with 1uF ceramic.

Bypassing the CONT pin as you have done may have more effect on the frequency if the supply rails are not adequately bypassed. 

You might also want to put a resistor in series with the MOSFET gate to limit the current, and to use a MOSFET that has low gate charge (don't use a huge MOSFET if you don't need to). 

Changes in the supply voltage during the cycle when the LEDs are on will affect the frequency so it would be better if the TLC555 was supplied with a separate regulated supply, or at least an RC. 

Many of these effects can be reduced if you hang a flip-flop or two on the output and run the oscillator at 2x or 4x. You'll also get much closer to 50% duty cycle. 

Unlike the bipolar 555, the TLC555 will give very close to 50% duty cycle with the configuration you are using, but the supply voltage has to remain very steady and the output reasonably lightly loaded.