JettsPapa

Changing six gallons in a 65 gallon tank won't have much effect. If you want to get nitrates down I'd recommend considerably more. The math is pretty easy. If you want to reduce nitrates by half you need to change half of the water. A 25% water change will reduce the nitrates by 25%.

First, I wouldn't feed Bacter AE. While I've seen some shrimp keepers say it works well for them, I've also seen an alarming of reports of it killing every shrimp in the tank. I have never used it, and my shrimp grow and multiply just fine. Even people who do use it say to feed much less than the directions recommend. Since they're in a tank with fish you don't really need to target feed them, but of course you can if you want to.

I wouldn't plant it in a 29 gallon tank. Cryptocoryne spiralis is another good option if you want something that looks similar to jungle val, but doesn't get nearly as tall. The only drawback is that it doesn't spread like jungle val (or at least it doesn't for me, and other crypts do).

You can let just about any aquatic plant float, at least for a while. Some people keep water wisteria floating, and it will do fine that way, but I plant mine. I just don't like the way it looks floating.

That shouldn't be happening. I suspect you have very low quality flakes, or you're feeding too much.

Shrimp

First, you mentioned a colony of endler's. Since you said the tank is for an inexperienced fish keeper I wouldn't recommend that. They likely won't want to deal with the fry. However, a group of all males would be a good option. Eight to ten of any of the nano shoaling fish (chili rasboras, ember tetras, celestial pearl danios, etc) should also work.

160 ppm is pretty high, though I think that 20 ppm safe level is overly cautious. You said you did two water changes. How large were they, and how much did they reduce the nitrate levels?

Guppies do okay for me when the air temperature gets down into the mid 50's, in 20 gallon unheated tubs, but I don't know what the water temperature goes to. I don't know if that helps or not. I don't think anyone can give you a definitive answer on whether or not you should add another heater without knowing how low the air temperature will get, or for how long. Is there any chance you could move them to a larger container? The water will change temperature more slowly with larger volume.

I have a dwarf Mexican crayfish in the 5-gallon tank on my desk with shrimp and a few guppies.

It's not a bottom dweller, but I was at 360 Aquatic in Houston a while ago and they had some leaffish (Monocirrhus polyacanthus). That's an oddball I'd like to get one day.

I'm just fine with anything up to at least 40 ppm. In fact, I add fertilizer when it's much under that level.

I'm not aware of any products to reduce nitrates, other than live plants. Water changes will help, of course, assuming your source water doesn't have high nitrates. You said your nitrates are "out of whack," but didn't give a number. What is the level?

Pearl gouramis would be a good choice. I don't think five would be too many (with mostly females, of course).

I'd stick with the honeys. Pearls are one of my favorite fish, but like honeys they seem to do best in groups, and I wouldn't mix gouramis anyway.

I doubt that plants will have any effect on pH. Welcome to the forum, by the way.

I of course can't give you an ironclad guarantee, but it's doubtful. Honey gouramis (and pearl gouramis) are generally much more peaceful than other gourami species.

Please define "ridiculously high." My water is 8.2 pH, and I have a wide variety of fish, invertebrates, and plants doing just fine. Unless yours is much higher than that I would strongly suggest you not "tinker" with it.

I'd recommend adding three or so more honey gouramis and call it good.

I haven't tried it, but the many posts I've seen from people who have lead me to believe they rarely work long term.

Done. The oldest already has a small tank. The girls are still too young (2 years and 5 months), but their time will come.

I've kept albino guppies (females are orange with a white band, and males are mostly orange with some random white). They're beautiful fish, but relentless fry hunters.

Does spending time with grandchildren count?

Welcome to the forum. Unless your source water has nitrates (and it wouldn't hurt to test it), then yes, I'd recommend you keep doing water changes until it gets down below 40 ppm. You probably already know this, but I wouldn't do them too often, or too large. You don't want to shock the fish still in the tank that have adapted to the high nitrates (and whatever else may be going on with a tank that was neglected for a while).

They don't need to be planted in substrate immediately. I don't think there's a hard and fast number, but it's quite a while in most cases. Probably at least several weeks. You'd probably want to get rhizome plants out of the pots sooner than plants that are typically planted in the substrate, but a few days certainly wouldn't hurt anything. I'm pretty sure they don't drop dead in the warehouse if they aren't shipped immediately after arrival. I don't know of any reason not to fertilize right away. And welcome to the forum.