The downregulation of acetylcholine receptors is indeed a concern although some people never have issues with this somehow, this is the primary reason I was suggesting breaks to make sure you're not getting dependent. I'm not aware of any mechanism whereby nicotinic receptors really contribute to regulation of other receptors without just influencing neuro transmission (for example, blockade of acetylcholine receptors leads to increases in dopamine flow, this is utilized in Parkinson's patients, and I imagine if chronic administration of an ampakine downregulated acetylcholine then it would result in a therapeutic increase in dopamine, while a decrease in dopamine at the start of acetylcholine stimulation would explain brain fog) but if Bobby has a source handy Id love to read it.
Oxi and ani are indeed mainly glutamate boosters, ani is almost an anti anxiety agent though while Oxi is very stimulating. Both will promote LTP, while long term DXM hasn't been shown to cause Olney's lesions or anything like that I think it is pretty clear the long term users do have deficits of learning and attention, and this is of concern. People with ADHD mainly have working memory problems, working memory is facilitated by D1 stimulation and NMDA, so I think antagonizing NMDA defeats the purpose of a racetam and an ADHD med, no matter what it does for acetylcholine receptors.
Also concentric exercise is actually pretty important, it's been shown to be vital for healthy connective tissue. I'm surprised you're not interested in grow hormone secretatogues, they are very interesting and I would use Ipamorelin + MOD GRF 1-29 myself if I wasn't afraid of needles. They can be used at a rate that doesn't desensitize growth hormone receptors easily. The main problem is actually that most of our growth hormone sits in the pituitary and decays there without ever being released, GHRH/GHRP just signals it to release before it breaks down. They have even been shown to improve one type of memory in the elderly.