Please continue to feed critical and water round the clock every 2 hours during the day and at least once at night; add probiotic to the water so he gets as much as possible ot help stabilise his gut. Your piggy is not in any danger of dying but it needs your ongoing support to get him through this.
Digestive Disorders: Diarrhea - Bloat - GI Stasis (No Gut Movement) And Not Eating
The poos reflect what has gone on 1-2 days ago. Stringy poos do not mean that the gut is closing down, but they are a sign that the gut is dysbiotic (i.e. the wrong kind of bacteria has taken over) as fibre is not fully broken down, hence the strings.
Unfortunately piggy guts are rather delicate and can react strongly to antibiotics that do not only attack any infectious bacteria but can also affect the ones that are crucial for the digestive process. Your piggy is on two very strong antibiotics so gut issues don't come as a huge surprise. Marboflexin is known as marbocyl in UK; it is related to but stronger than baytril (exroflaxacin) and chloramphenicol is the strongest antibiotic you can use for eye problems.
The size of the poos means that there is still a reasonable amount of food being processed, so that is good. Keeping the gut going and the feeding up is #1 priority.
You may want to contact your vets tomorrow re. gut stimulants to help with the bloating (as it is Sunday today). If it gets worse, contact an out-of-hours vet or a 24/7 clinic today, ideally during day time hours as that is cheaper if you have one within reach. Please be aware that probiotic takes some time to work, as do antibiotics; they build up over several days.
If you have a healthy companion, then 'poo soup' in combination with the bene bac can help to stabilise the gut as it is bascially life transfer of healthy gut microbiome if done correctly and more effective than probiotic powder. I don't know whether you can get hold of fibreplex in the USA? It contains probiotics but more other gut support and can help in cases of antibiotic related loss of appetite.
Probiotics, Recovery Foods And Vitamin C: Overview With Product Links
Hang on in there and try not to panic! Your determined care will make a huge difference and can see your piggy through this crisis.