Tip: No matter how much you like Electrum as a lightweight client, it sucks at Lightning.
The funds were deducted from my channel balance ("can send" is lower) but I don't see any history of actual payments.
Have the funds been received from the other party? Have you contacted with it since then? If they are, then the "can send" is reasonably lower.
I think there isn't a path from Electrum trampoline to my payment target. I want to close the channel and open a new one with another node provider but I'm not sure what will
happen to the pending funds.
Here's something that always clears up the situation: Back up your wallet, including your lightning state. Re-install it and retry.