Sorry to hear about yourself and your father in law's health.
It is your husband's responsibility to make sure that you are at ease and
comfort. To be honest it is a wise decision to make sure that your father
in law is beside his wife so that he can be looked after even better.
The only way to tackle this would be to make sure your mother in law knows
of this concern. Your husband is an ideal bridge and for this you must
speak to him very calmly and explain your concerns.
If this doesn't work you must then seek some counseling and or speak to a
local Aalim who can try and sort this out for you.
On the other hand, I find it wise to mention that your father in law has
rights over your husband and yourself.
Your husband is his son and he needs to make sure that he serves his
parents in the best of ways. This is something that Islam really
emphasises on to the extent that even the Holy Quran talks about this.
(sura al-Isra ayah 23)
You as s Daughter in law, now have an independent relation with your
father in law regardless your husband. Did you know that one's father in
law is his/her mahram for life even if the husband wife separate?! In
that case you need to closely look at this and make sure you're neat on the steps you plan on taking.
I hope your issue is resolved and your father in law feels better.