Umm, a "Scout", eh?
Never have seen one that I remember.
But I think there's one unintended clue in your description:
also it sems like the tubes are glowing more than before
If you mean that the outer gray or black structure inside the tubes is showing color, that's a sign of two possible things:
1) You have already overheated the tubes enough to damage them.
-- OR --
2) You will, if you keep it up.
Big, "transmitting"-type tubes like 3-500Z, 572B and 811A will all show some "cherry" on that plate structure when running full bore. Those types are built from materials meant for a higher operating temperature than small tubes adapted from color TV circuits.
I'm assuming your Scout has eight 'sweep'-type tubes, meant for use in color TV receivers. The plate on these is NOT supposed to show color. How long you key it will affect this, as well as how hard you drive it.
Either way, if the plates on those tubes "cherry" AT ALL, the life is (or was) draining out of those tubes by the second.
I'll predict that some small (soldered-in) part that controls bias voltage on the driver tubes has failed. Typically a 20 or 30 year-old electrolytic capacitor will wear out and short. This blows out the black plastic rectifier diode that feeds it. Now the tubes have NO fixed bias voltage on them. This causes the tubes to pull more current from the power supply than they should. The extra heat just gets dumped onto the tubes' plates. Enough excess heat and they'll glow. First a dull red, then brighter. Before they can get to orange, the fuse should already have blown.
I'll give you credit for one thing. You skipped the next step in this process. What usually comes next is the owner will cuss the last "correct"-size fuse he had, and puts in a larger size.
When that one blows out, larger fuses get put in, until eventually the circuit breaker for the building's outlet circuit trips out.
By then, so much smoke has been let out of it that the repair estimate gets out of hand.
Even if all you've damaged is tubes, that won't be cheap. Unless it was made with "orphan" tubes with high heater-voltage ratings, like 30KD6, 31LQ6, and such types. Some of those are still cheap.
If it uses the more common 6-Volt heater tubes like 6MJ6, 6KD6, 6LF6 or such there will be sticker shock, if you haven't shopped for those in a decade or three.
And if it was made with the, er, "industrial" 4-digit tubes like 8950, 2057 or 8098 tubes, the sky's the limit.
Maybe the tubes are still okay, but it doesn't sound like it.
And if you install new ones, don't let them "cherry". But if they do, it would prove that there are other faults remaining in the amplifier besides just failed tubes.
73