It looks like he has some bumblefoot infection on his foot. The comb looks like it may have been pecked or injured. Do the comb and wattles appear swollen to you? It is hard to see in the pictures. What are you feeding the rooster?
I can’t really tell much about possible gout or mycoplasma synovitis from your pictures. The picure below is possibly mycoplasma synovitis which shows swollen ankle joints:
You'll get excellent help from the folks here, but I'll just chime in to answer your original question: Injectable antibiotics may be less likely to cause sour crop than oral ones, but a lot of it depends on the specific drug in question. Some drugs are about equally likely to cause gut flora problems, regardless of how they are administered, while it'll make a significant difference for others. He'll need at least a week of probiotics after he's finally off the meds to get his gut flora back in order.