Ah, were I courageous enough To shout Stuff your pension! But I know, all too well, that's the stuff That dreams are made on: (21-24)
The speaker wants to tell his boss to stuff it, but he can't. He lacks the courage necessary to do it. And not only that, he knows that the courage he lacks is the courage necessary to make dreams become reality. He knows that it is his lack of courage, not just that toad work, that's truly responsible for his inability to realize his dreams.
For something sufficiently toad-like Squats in me, too; (25-26)
We've all known or have heard about people who do whatever it takes to achieve their dreams or their goals. Sometimes that indicates positive personality traits, like perseverance, and in other cases it indicates negative traits, like cheating or lying. Whatever the case may be, this speaker's internal toad, the thing that's squatting in him, is what's keeping him from doing what it takes to get what he wants.
And will never allow me to blarney My way to getting The fame and the girl and the money All at one sitting. (29-32)
Well, it looks like that internal toad is keeping our speaker from being dishonest or insincere in pursuit of his dreams. That sounds like a good thing, right? But our speaker doesn't seem too happy about it. Sometimes it's tough to do the right thing. And sometimes it means that you miss out on something you feel you deserve. Sometimes that internal quality that makes us do the right thing can feel less like a blessing and more like, well, a cold, slimy toad.