Floppy Rabbit Syndrome and head tilt, are really two different illnesses. True FRS is most often caused by some sort of temporary nutrient imbalance, possibly low potassium, but no one really knows, just that almost always the rabbits can recover fully with the proper care. The primary symptom is the whole body is flaccid and the bunny can't move it's limbs, but is still very alert and willing to eat, and there is no head tilt. With regular feeds and supportive care, mobility starts to return within a week or two, and the rabbit recovers completely.
Head tilt is more to do with vestibular disease and balance issues, most commonly due to either an inner/middle ear infection or the parasite e. cuniculi, occassionally toxoplasmosis if the rabbit could have been exposed to cat feces. If e. cuniculi is involved, there can also be paralysis, usually just the hind limbs.
http://www.bio.miami.edu/hare/paresis.html
https://wabbitwiki.com/wiki/Head_tilt
To tell the difference between a rabbit that has paralysis due to e. cuniculi or FRS; rabbits with EC are usually much worse off and will usually have some head tilt or other problems with their head like nystagmus, whereas a rabbit with FRS may seem pretty normal except for the fact their body won't move. They can hold their head up and eat and act somewhat normal behavior wise, and within a week or two their mobility will have returned and they will be back to normal. A rabbit with EC will have more problems, will usually just have hind limb paresis, may have head tilt, nystagmus, vertigo, roll, fall over, and usually recovery will be much slower and they may not recover mobility or recover at all. There are other causes of paralysis too; like spinal trauma, sponylosis, roundworm parasite, heart failure, toxins, toxic plants. There can also be the possibility of tumors or cancer, especially in older rabbits.
If you look at these FRS videos, the first one does look like FRS, the second where the rabbit won't stay upright, isn't moving it's head, and is falling over, that isn't FRS. Something more serious is going on with that rabbit, either EC or possibly heart failure. The bottom two videos could possibly be FRS, though other symptoms need to be taken into account, as well as other possible causes for the flaccid paralysis.
https://wabbitwiki.com/wiki/Paresis_and_paralysis
If there is any chance your rabbit doesn't just have FRS and it could be EC, spinal trauma, or another cause, please have your rabbit properly evaluated by an experienced rabbit vet, right away. If there is possible spinal trauma, there's a chance of recovery if steroids are administered in a short time frame following the trauma. If EC is a possibility, the best chance of recovery and reversing the cell damage causing the symptoms, is with the proper medications(antiparasitic, anti inflammatory, antibiotic cover, supportive syringe feeds).
If your rabbit doesn't have full paralysis but is falling over losing balance, this could be due to an ear infection, which would need xrays possibly, and the proper antibiotics prescribed, as well as anti inflammatories(meloxicam). With him having a weepy eye previously, there is a chance it's related. Both ear infections and EC can cause weepy eyes.
https://wabbitwiki.com/wiki/Encephalitozoon_cuniculi
Medirabbit: ear infection clinical signs and treatment
https://rabbit.org/vet-listings/