We're told concerts for "Tom Sandoval & The Most Extras" have been a big hit amid all the drama. For example, their show at the Wolf Den at Mohegan Sun Casino & Resort in Connecticut earlier this month had a massive turnout, marking the first time the venue's had people lining up to get into a 350-seat theater.

Tom's crew sold out the Gramercy Theater in NYC the following night, with the line wrapping around the block -- even 'SNL' star Chloe Fineman got to meet Tom backstage after the show. We doubt she waited in line.

Tom's band also sold out shows in Pennsylvania and Texas. Their Houston venue, in particular, expected 1,000 fans to show up, but was instead bombarded with twice that number ... making it one of the club's most successful shows ever.

The band even rocked a fundraiser on May 11 at DC's Howard Theater, where they donated $10k to Drew Strikes Back ... an org that raises money for the Leukemia & Lymphoma Society.

We've also learned Tom hit a big milestone during this recent stretch of shows ... celebrating 50 days sober.

Tom tells TMZ ... his recent fallout with Ariana Madix has been a difficult and emotional thing for him to navigate, adding he's been in "some really dark places at times and music has really helped me get through it."

He says he's grateful for the big turnouts and is excited to keep the second leg of his summer tour going for him and the group.

Of course, Ariana's been doin' pretty well on the other side, too -- not only does she have a new boo, but she's been striking brand deals with SoFi, Raising Cane's, and even a sex toy company!