Frame strength/flexibility

zzzzhjv456 said:

I have a question about my bike. A twitter Blake MTB,

Click to expand...

Which one? http://twitter-bikes.diytrade.com/sdp/2186288/4/pl-7061566/0.html

zzzzhjv456 said:

I am trying hard to raise my natural cadence from the low 80's, But every time I get above 85RPM, approx., I start to get bounced out of the saddle by the bike. It kinda feels like riding a kids bouncy castle or a space ball, if you remember those lol.

Click to expand...

I can pretty much guarantee it's you and not the bike.
Get shoes and pedals with a shoe-retention system.
I recommend any of the SPD lookalikes. Wellgo will do fine.
Start practising one-legged riding. Doing only 30 second intervals as a start will be fine.
This will mercilessly force you to figure out how to pull the pedal UP too as opposed to merely keep pushing it down.
Also, the shoe retention system will keep your foot in place so that you don't need to keep a downward pressure on the pedals to prevent your foot from slipping off.
Once you've figured out how to get the upward-bound leg out of the way by its own power as opposed to being pushed up by the downward bound leg you'll soon be sitting steadier in the saddle.
Even if you decide not to use shoe retention on your regular rides, this training will still help you to keep from bouncing.

zzzzhjv456 said:

I also get this when going over uneven, as opposed to bumpy, roads, where it's not necessary to get out of the saddle.

Click to expand...

For that situation, tire pressure and/or suspension settings CAN play a part. You're not saying what you're using, and I can't tell from here.
High tire pressures help keep the rolling resistance down, and prevents pinch flats. But for traction, control and comfort it's important to keep pressures as low as possible while still avoiding (too frequent) pinch flats.