What is the ruling on the viscous fluid that was discharged, and does it necessitate ghusl or not, and how should one pray and perform tayammum when unable to perform wudu or ghusl due to illness, and what is the ruling on missing the Fajr prayer in this situation?

It appears that the fluid mentioned is semen, given its description. Since your doctor forbade you from washing, your ruling is to perform tayammum (dry ablution) while washing whatever parts of your body, including those of ablution, you are able to. When you recover, perform ghusl (full ablution), and you are not required to make up the prayers you performed with tayammum.

As for the second part of the question, you should not return to sleep after waking up and after the time for prayer has begun, as this involves negligence and leniency. You must repent to Allah if you deliberately delay the prayer beyond its time.

If "praying on the bed" means praying without standing, then it is not permissible except in cases of inability to stand, because standing in obligatory prayers is a fundamental pillar.