ISO Ideas for 2yo former MSPI with continuing sensitivities - where to turn next? (LONG, sorry!)

Sorry this is long - I don't know who other than you ladies might understand this or have ideas, goodness knows the docs involved do not! 

DS is 27 months, dx with MSPI (eczema, gas, mucous and blood in poop) and reflux at a few weeks of age. I was nursing and went on dairy and soy elimination (and participated in the MSPI Check-in!). He had horrid colic for his first few months of life somewhat alleviated by my diet and Zantac, and better with Prevacid started at 6 mos.  Transitioned to Alimentum at 9-10 months.  Weaned off Prevacid at 12 mos.  Dairy trials starting shortly thereafter tolerated baked dairy in moderation but not other dairy like cheese, yogurt or milk (cooked cheese on pizza and in other things also not tolerated) -- he got a rash on his cheeks and nasty diaper rash, and with milk lots of gas and diarrhea.  We stuck with baked dairy only and in moderation and from time to time tried other dairy with similar results.  He's been drinking almond milk since coming off Alimentum at around 16 months.

Visit with allergist at 18 months and he tested negative for Top 8 plus a couple seasonal allergens via scratch testing.  Per the allergist, serum testing not recommended and we should slowly add dairy products to his diet.  By 20 months he could take small amounts of yogurt and an occasional mac and cheese.  This past summer he was eating lots of fresh fruit, a small amount of yogurt some days, and mac and cheese maybe once or twice a week.  He did have occasional sudden-onset diaper rashes that could not be traced to clearly to dairy (i.e., it sometimes would start 72 hours after having mac and cheese and not having yogurt in that time) but they would clear within a day or two.  The only soy in his diet is scant amounts of soybean oil in occasional prepared foods, and no correlation to be seen when consuming that.

Fast forward to late November.  DS' picky eating hit a zenith, and it became harder and harder to get him to eat a reasonable meal.  Starting the week after Thanksgiving, he developed a very sudden and very nasty diaper rash from front to back - it looked like he had been scalded and every diaper change was a nightmare.  No change in diapers, etc., and he had not eaten anything at Thanksgiving dinner (literally) and had not had an excess of even baked dairy in that time.  He is changed a ridiculous amount for a toddler - I'd say about every 2 hours if not more sometimes - so we don't think it is entirely from the moisture in the diaper. 

We chalked the rash up to a freak occurrance and treated it with our usual regimen.  No eczema or diarrhea.  We pulled all dairy from his diet and limited baked dairy and incidental soybean oil, and stopped other potential irritants like tomato and berries.  It took 2 weeks for the rash to clear.  Once clear, we started back with his former levels of baked dairy.  All was well.  Then we started back with occasional berries (like strawberry jelly) and one serving of mac and cheese.  All was well for a few days (during which time no more dairy or berries were given), and then the rash came back worse than ever.  This time it went from healed skin to scalded looking skin with tiny bleeding spots within hours.  Of course, once the skin was broken, within a day or so he got a yeast rash on top of the existing rash.  He could barely sit down.  This is now mid-December.

We used every rash treatment product you can think of, plus yeast treatments, diaper-free time and sitz baths, and it just would not clear.  We went to the pediatrician, who recommended drying his bottom with a hair dryer at every diaper change, and using a mix of zinc oxide, lotrimin and hydrocortisone.  We did that and changed to chlorine free diapers.  The rash flared up and got lighter back and forth many times.  We were and are basically tethered to the house in order to handle the treatment regimen.  While it cleared a little, it never really went away.  The poor kid was now afraid of diaper changes.  His diet remained free of dairy, soy, berries, tomato and cinnamon (a late add that we cut out just in case).

2 weeks ago I returned to the pediatrician as this was getting ridiculous - it was hard enough to feed him before given his pickiness, but his pickiness plus the restrictions meant he we were literally feeding him the same thing every day as it was all he would or could eat.  And the rash was still there, and putting hydrocortisone on his skin every day was making me uneasy.  The pediatrician recommended that we go back to the allergist.  So we got an appointment and went back to the allergist, who looked at the rash and said it was not from an allergy, but perhaps a sensitivity, and that we just had to adjust his diet.  I lost it, as there is no more adjustment to make with a picky eating, 10th percentile for growth 2 yo who I was begging to eat chicken nuggets to get protein in!  But he said that he would not do more testing as it would not tell us anything about sensitivities, and we just had to base what we were doing on his symptoms.

So last week I went back to the pedi for suggestions on what to do.  She had no idea and recommended we see a gastroenterologist and get worked up for EoE.  From what I know about EoE, the symptoms are more "above the navel" than below it -- meaning we don't have swallowing issues, vomiting, etc.  that I read about with EoE.  So that did not make sense to me off the bat.

This week the rash is looking better, is more localized to a wide "ring" formation (rather than there and across his buttocks and all the way up to his groin and scrotum like it was) and is much less distressing for DS.  We are starting potty training in the hope that will help with future rashes - but that is a long term solution and it does not solve the problem of what is causing them in the first place and what we can do about this and his food intake in the short term. 

If you have not utterly given up after this novel, here is the question - where do I go next?  Is this logically a problem for the GI?  Does it make more sense to see a different allergist for a second opinion before going to a GI?  Or is my pediatrician the one who needs replacing?  I want some answers for DS, as he has had a pretty miserable couple months and it is frustrating to no end that I can't help him more.

Thanks for any ideas you have (and for tolerating the length of this post).