Codes C1252, C1256, C1259, C1310, Prius 2005, 220k m, how to DIY?

Hello Prius experts!

My 2005 Prius has these codes now:
C1252 - hydraulic-booster pump motor malfunction
C1256 - accumulator low pressure switch malfunction
C1259 - HV system regenerative malfunction
C1310 - malfunction in HV system

History: May 2016:
TOOK TO DEALER IN GAINESVILLE FL - BRAKE ACTUATOR NEEDS TO BE CHANGED (SOMETHING THAT COST OVER $2K

Drove to Orlando (entered in limp mode for the first time after, 60 miles) for a second opinion. In the last few miles the HV battery was not charging.
BIG BATTERY CHARGES UP QUICKLY AND DISCHARGES QUICKLY - SOME LIGHTS HAVE COME ON - AND SOME TIME THERE WAS SOME BIGGER NOISE THAT STARTED FORM THE ENGINE - NOW THE BATTERY HAS STOPPED CHARGING

BRAKE PEDAL WAS HARD TO PUSH - THERE IS A BARKING NOISE FROM THE BRAKE MODULE.

TECH NOTES (copied from the repair shop paperwork): SCANNED ALL COMPUTER MODULES- -
P03000 BATTERY CONTROL SYSTEM - -
P0A80 REPLACE HYBRID BATTERY PACK - -
P3014 BATTERY BLOCK 4 BECOME WEAK - - ALL THESE CODES PERTAINE TO THE HYBRID BATTERY - -

C1252 HYDRO BOOST PUMP MOTOR FAULTC
C1256 ACCUMULATOR LOW PRESSURE FAULT - -
C1259 HIGH VOLTAGE SYSTEM REGENETIVE FAULT - -
C1310 FAULT IN HV SYSTEM/ FAULT IN ACTV BOOSTER SOLENOID - -
C1391 ABNORMAL LEAK OF ACC PRESSURE - - MULTIPLE CODES FOR BRAKE ACTUATOR - - THERE IS A TSB FOR DIAGNOSTICS ON THIS SYSTEM THAT STARTS WITH BLEEDING THE SYSTEM AND PERFORMING A RESET AND THAN TESTING FROM THERE - - -

RECOMMENDED REPLACE HYBRID BATTERY WITH FILTER AND THAN PERFORM TESTING FOR BRAKES TO ELIMINATE SOME OF THE VARIABLES- - SUSPECTING FAULT IN BRAKE ACTUATOR - BE PREPARED

I refused (of course) and start educating myself for DIY repair.
Drove back to Gainesville (130 miles) in limp mode with ABS, VSC and BRAKE lights on and red triangle, with several stops. When starting, HV battery was charging several minutes (around 10 min) after than stopped, however I was able to drive with drained HV battery (only on gas).

Found one bad cell (6.8 v instead of 7.6 of others) in the block 4 and replaced ($40 from e-bay).
Bought a scanner and checked: only the four codes (in the title) remained, all other disappeared.

Later I noticed that if I disconnect and connect the 12 volt battery, the charging level on the screen jumped from 1-2 bars (when disconnect) to almost full. If I clear the codes, warning lights, red triangle and hard brake pedal disappear after starting the car, however, after some minutes they appear again. The hard brake pedal disappear randomly even if I do not clear the codes.

Kindly share please your thoughs. Thank you.