Hello, and welcome.
My heartfelt condolences on the recent passing of your older girl. I'm sure you gave a wonderful life!
Regarding your 4 year old male, it sounds like he's improved compared to 2 days ago, but if he is still unsteady on his feet, he may have a condition called vestibular syndrome. This is usually caused by an infection or other disturbance in the middle or inner ear. The vestibular system controls balance and equilibrium, so if something is off in that area, it will make a cat feel dizzy, not be able to walk straight and very often the dizziness will lead to nausea.
The fact that he is hungry and is eating without any more vomiting, is great, in addition to him wanting to play a little bit. However, he does need to be seen by the vet in person so you can get a diagnosis and treatment. Try to get him in, tomorrow, since you're off and don't have work.
I hope all will be well with your furry boy and please let me know how he's doing and what the vet's findings are. Thanks!
Please be so kind as to rate my answer with positive feedback; that is the only way I receive credit for my assistance. Thank you very much!
Providing a positive rating will not end our conversation, should you need me for any follow-up. Simply click 'Reply' for clarification or additional information, if needed, and I will be glad to continue at no additional cost.