I think both your boys are doing amazing for their age!
It must be a bit of a shock to have a double whammy like that when they have been so healthy for so long.
It does seem a bit odd if they were that overgrown before because he wouldn't have been eating ok and would have lost weight. He also would have been pawing at his face from the discomfort.
With regard to checking teeth, it depends on how easy it is for you to look and whether it distresses them. If it's not easy for you to manage and/or they don't like it I'd monitor daily how well they take a seed. It's usually a good indication of teeth issues. If they can't eat it properly i.e they take too long and keep dropping it or can't crack the shell then you need to check more thoroughly. I would try and actively check every 3-4 days if you can, but it really does depend on whether they play ball. It's one of the reasons I check with seeds as it's a lot easier to monitor. I'm not sure if anyone else has other advice or disagrees?
I know that when my gerbils have lost teeth and the other front tooth has continued growing they have been capable of working harder to wear the longer one down without the need for trimming. I have always raced to the vets and apart from having metacam to help relieve the pain and discomfort, they have left them to see how they manage. Each time they have sorted themselves out like the clever little things they are.
You are doing all of the right things by adding more for them to chew. Different textures help as it gives them more interest and they tend to chew for longer. I also found putting in softer things grass houses or the carrot and hay covered cardboard houses and tubes went down well because it was more comfortable for them.
I completely understand with the scent gland tumour and to be honest at that age, even if I had the money, I don't think I'd be risking it. If it's not causing any discomfort and Clove is messing with it and it doesn't seem to be growing then I'd say it's best to leave it well alone. Please don't be embarrassed about not affording surgery. We have had a few discussions about the cost of scent gland removal on here. It has now become silly expensive in a lot of places and it's not something I can afford currently.
Also both of my boys tumours appeared very fast and we handled them lots and did daily checks and it still came as a shock.
The exotic specialist we went to initially gave us loxicom to see if the lump went down. It may be something you could ask your vet to try to see if it makes a difference.