Then I advise you to go to varanustalk.com and read...you will find very quick that a 6ft cage won't be big enough for a full grown Sav, you will also see you need a tank that can allow 2ft of compacted dirt substrate so that they can burrow down. It is better to have a bank of 3 lower wattage basking bulbs that create a hot basking spot that covers the entire length of the animal without heating up the rest of the cage and spiking your ambients...crickets aren't the best source of nutrition for any lizard...at that size he should be able to eat pinkies with no issues, him not eating and the lump on his back is cause for concern IMO and I would look at taking him to a vet and fixing your husbandry issues asap
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