I don't think that your cable sheath has adequate pressure rating. So even if you do take a packing gland approach you stand to have leakage.
By the way, you need to be extremely cautious if you are planning to pressurize the conduit. You may be running into safety regs and increasing the risk of injury to your maintenance crews.
Case in point is that the electrical codes do not consider conduit as "pressure piping", yet that appears to be the focus of your question.
If it is pressurized then you need to conform to the piping codes such as B31.3 (as a minimum) and have provision for safety relief in the event of fire, etc.
Electrical feed throughs are available for process feed throughs.