Update:
Wow, I can't believe it's already past the 'half-year' mark since posting this originally. From a distance and being further away from everything, objectively it feels like not much has really changed or improved. My mom has been breaking down and crying nearly as much as she did before, and I get almost daily calls from my brother who lives behind them with rants about the next thing my dad has latched onto.
He has been on Lexapro and over the past several months has had his dosage increased from 10mg to 20mg. Yes, the symptoms are subdued where he may seem a bit calmer and restrained (demeanor wise) but he still has very little self-control in terms of expressing his anxiety and controlling his thoughts. Symptoms are no different from before in that he is worse in the morning and 'better' towards the mid-late afternoon and evening.
My mom finally conceded to having him see the psychiatrist about a month ago - the psychiatrist sounded hopeful in that he just needs to maybe increase his dosage and he'll turn a corner in June/July? He diagnosed him with moderate anxiety and depression. So far, no corner has been turned from what I can tell. I have a friend who went through depression and told me he had to 'experiment' through a round of different anti-depression drugs before he found a combination that worked for him, so he was warning of a long path ahead.
Just this AM, my brother texted my other brother and I, saying we're going to have to consider a "living rotation" with my parents or hiring care for my dad. Apparently my mom called him and broke down (this has happened more than once btw). My dad had woken up at midnight, complaining about hearing scratching sounds outside then started spiraling into how they have to worry about selling a rental property they own and how, because of the "poor condition" it's in, it'll make my mom look bad because she's a "public servant" who works at the school district. Whaaaaaat??? But yep, this is just an example of the things my mom and brother are currently putting up with. My mom remains hopeful but it's hard to see any progress. My brother is getting more and more stressed out dealing with him and then dealing with being the point person for selling their rental property so it's taking a toll.
Oh, the other thing that I think is really messing him up still is his diet - in fact, they just saw the endocrinologist (I think) and he was told that it's OK for him to have cheat days to eat steak, pizza, whatever he wants, etc and that he *needs* to so he can gain some weight back. He's not having it though - he thinks the doctors are wrong and that what he Googles is correct :T So he's in a pretty messed up state of mind. He has lost at least 20lbs or so and started slowly gaining some of it back but it seems like he's more so just maintaining the weight.
Through all of this he has been seeing a psychologist who I'm starting to think isn't that helpful at all. The basis of the 'therapy' is "you have to acknowledge you're having some kind of issue, then you need to face your fears" but it almost seems as though it's left at that with no practical application - it's a very generalized kind of help that isn't actually helpful to my dad because my dad just keeps saying stuff like "We have no options. I'm stuck. I acknowledge there is an issue but I don't have the answer and I don't know what to do even if you tell me what the answer supposedly is" - on top of that, he'll make claims about things that he can't substantiate: "We're not going to be able to sell the rental property - we have to get it into better condition because nobody will buy it" which isn't true because it can be sold as-is to someone looking to fix-up, or "We can't afford to buy anything - we don't have money" even though they bring in a low six-figure income from pensions, social security and my mom consulting. So apparently his anxiety and depression are causing him to believe in things that are actual realities to him but not rational or true at all. Or he'll spiral into worst case "what if" scenarios and go down those rabbit holes. He says he's "aware" of these things but can't stop himself. The most frustrating part is that you might know exactly what he should do to resolve something yet he won't believe it - so he basically thinks there are no answers to the "problems" he's having. And you kind of have to push forward in making decisions on his behalf etc. The latest example of this that I've alluded to is selling their rental property - he thinks they have no money to put into renovating it for resale, then spirals into how if they were to sell it they'd get hit with huge capital gains and the end result is that they'll have no money. A lot of his concerns revolve around not having any money left - it's odd. My brother has had to pick-up most of the responsibility for working with realtor and getting bids from contractors on the place through all this, while my dad continues to complain in the 'background'
Anyway, I can't help but think it's more than just anxiety and depression. Or if it is, it doesn't seem "moderate" to me. Then again, as I've never personally experienced this I wouldn't know. It's probably one of those things that's much more difficult to go through than it sounds, where perhaps to someone who doesn't know much about the topic it may just sound like a side comment: "oh he just has some depression that he's going through that's all" - at the very least, it's been an eye-opening experience (not in a good way). I'm just wondering if we ought to consider a second opinion or something. Already, it feels like he has seen so many doctors though... you kind of wonder how many more it will take to get a "right answer" if none of them seem to know what the issue is.