Yes that still sounds off to me, for so many reasons.1) It's completely unnecessary - "used to" or just "worked part-time" would be fine 2) "would often" is usually used to indicate nostalgia 3) Working part-time is not a regularly repeated event, it's a state you are in. You don't say "I often work at Hitachi," as in individual days, you say "I work at Hitachi". 4) It's incomplete - You worked part-time where?
"I would often help out at my uncle's shop" would be fine. It is indicating a regularly repeated number of days and indicating nostalgia.
Btw the earlier sentences using "sure" and "surely" were all great! "I'm sure" sounds much more certain than "surely" though. Again, using "surely" indicates you are trying to persuade others of your opinion, that in fact you are not completely sure of something.