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The only course of action here is the use of good penetrating oil. You can mix WD40 with automatic transmission fluid to make a good penetrant. The key to success is liberal and frequent application. DO NOT attempt to use the steering wheel to force the cable end thru the tilt tube. You will break the helm gears.
Back the big nut holding the cable housing to the tilt tube, and keep spraying the mixture in from both sides. Disconnect the steering rod from the cable eye and insert a thick shanked screwdriver into the hole and carefully rotate the cable end back and forth., but no more than a quarter turn in each direction, while applying the penetrating oil. Then let it soak and repeat. Once you get the cable free, pull it completely out of the tilt tube and clean both the cable end and tube to get the corrosion build up off/out of the two parts. Apply marine grade grease before you reassemble.
Sometimes, replacement is the only option. If you apply heat, be careful. That tube is aluminum and melting is a distinct possibility.
Was the cable stuck from the start, or was the wheel turned to the right and it got tight and then stuck?