Reading what you have posted there are a number of things that pop out to as issues that should be addressed different ways.
One aspect sounds quite a bit like you have a Parent who wants to change the way the Den and Pack work to cater to their Scout. This is not that uncommon a problem, and while it does require an increase in the level of effort an attention applied by the Committee, your Pack will be the better for the steps taken in the long run. It is important to clarify the Pack’s budget and what is paid for by the Pack vs the Family. There should always be language about reimbursement requiring prior expense approval for the dollar amount and purpose with a Committee vote on anything above a CM/CC discretionary amount of $25-50. It is possible to say the Pack will cover only the rank required belt loops and “x” electives in your bylaws but it needs to be formally written in, clearly communicated (and adding an explanation that the Pack wants to keep individual costs down to what is being planned for the year would be a good add on if this is done), and then applied to everyone exactly the same. What the Pack does and does not cover should be written up formally (Pack covers X recognition items, costs for Y event, family responsible for Uniform, Pack/Den dues of X, fees for all events other than previously mentioned, etc) I personally feel that Packs should budget in for Scouts to earn all the advancement available, but our Pack did clarify that we cover all rank related recognition and Pack/Den scheduled award/event patches but not additional activity patches.
The next thing I see from what you have written sadly looks like the Parents being interested in a program that is the least amount of effort for them to have their Child go through the motions earning rank. (I would be happy to be wrong!) Meeting twice a month is more normal than unusual in my experience, and in line with the program structure. One idea here would be to have the first meeting be an advancement activity and the second be an elective activity. I am not a gambler, but I would bet that if you run engaged meetings the Scouts will want to go to both (which is part of the point). Yes you need the parents involved, but it’s for the Youth. Are any of the competing activities only once or twice a month? How are they going to deal with the Troop level where meetings are weekly plus weekend activities? With the other Scouts not wanting to participate due to seeing someone else doing more sounds like in part them not getting the program they want. There is nothing at all wrong scheduling what will be done in the Den, and actively promoting the rest to be done individually. I have always tried to focus on providing opportunities for all the rank requirements before Christmas, but there are always things that come up with some individuals missing things, and others who go to Camp knock everything out early. A Den active over the summer can easily earn rank in Sept/Oct and focus on electives and awards (anyone doing NOVA awards? Hit me up if you are interested in help with them) Remember that we are Facilitators and gate openers rather than gate keepers, if the Scouts are engaged well with abundant opportunity there is less to look at in what others are doing/getting.
The discipline is a tougher one, and is likely to require more leader attention unfortunately. Policies need to be clear but supportive and consistently applied to all Scouts. Policies of a Parent being with their Scout as they run their derby car may be appropriate to prevent problems as an example. (I have seen excited Scouts dance and trip plenty of times…)
One program question for you; How many of your Scouts have earned the Outdoor Activity award? (This year is much harder with the pandemic of course) If it’s not a decent number adding some focus on it may help your Pack. It’s one of the items that is kind of like the JTE metrics; units that work well tend to hit them without trying and units that work less well and strive to hit them become well functioning units.
This got long in a hurry…