Too weak for most of the series

Within this forum it seems the advise is to go as far as you can in the TB series and just keep working at getting further into it.  In the tutorial videos however, it was suggested that if you can't do a bridge or handstand you can do some of the later work standing on your feet with your hands on the wall behind you.  I've been doing this inverted variation and it seems to be helping.  Am I wrong to continue through the whole 45 minutes with my feet on the ground?

Related to that, I lack the core strength to do the supine curls with legs straight, so I've been doing them bandless, with my butt right up against my heels, finishing the reps with some assistance from grabbing my thighs.  Am I wasting my time?  It seems like this will both improve core strength and mobility, focusing on laying down and picking up one vertebra at a time, but let me know if its better to skip the movement entirely until I can do it straight-legged.

Hey again Jessica,

You are 100% okay to scale the elevated bridge work by having your feet on the ground. I do suggest submitting a video to check your form on those scaled versions. 

Can you please post a video of your modified supine curls as well? The main focus of the band curls is to work on shoulder flexion and train the middle back/traps. 

Here's my modified supine curls.  Really I'm only working abs so perhaps this one I should skip.  

And here's my modified thoracic pushups.  

Your feedback is appreciated.

HI Jessica, I like your push up for sure, you seems to have a good mobility. for the spine curl begin with bent knee puts too many pressure on the lower back, in fact in the video the band pulls it is made with straight legs. if you cannot to them with straight legs consider to put something under the upper back so that you reduce the range of motion. but keep the legs straight.