Since the rabies has the most potential for reactions, it should always be given separately. Corona causes reactions and isn't necessary. Before I knew anything about vaccines, a vet gave Ellie way too many in one day and she had a very serious reaction.
Are his gums pink or gray/white?
If they are anything but pink he needs to go to the ER.
Some pain and lethargy can be normal but he should be able to stand and he really shouldn't be shaking.