5000 calories in 7 days (714/day) is WAY to little for you. But, due to stress, that's understandable (is the Infidelity Diet). Just don't keep it up long term (>1 month or so). With that calorie deficit, you WILL lose muscle mass. You're basically starving.
Also, eating once a day is also not good, especially if you are diabetic (Type I or II? if II, your problem was likely your weight, which you've "solved." Bravo!). It's much better to eat smaller meals more frequently (like ~300-400 cal/meal * 5-6 meals/day).
It's a bit counter intuitive, but when you starve yourself, your body actually tries to retain every calorie it can as fat, but will breakdown muscle for energy. In the end, you lose weight, but are "skinny-fat;" same body structure as before (muscle to fat ratio), but just smaller. When you're working out and eating a bunch, your body actually gets less efficient and doesn't absorb/retain all those calories. It's why football linemen have to eat 10-12K calories a day. They aren't burning that much; their body is just poorly efficient.
For loosing (or gaining muscle), you want to aim for 1-2% of your body weight/week. If you are loosing more than that, bump up your daily calories by 100-200; you are aren't, cut the calories by that amount. You have to be somewhat Zen about it, there's no magic formula.
If you knew/know that, my apologies for preachin'. Also, you've got to get out of the shock phase of this, so do/eat what you can. Just don't run yourself into the ground.
On the weights, that's some good ingenuity you got going. Some suggestions I'd make, as you are looking to build your gym, are:
Kettlebells: Rogue fitness has good prices. I recommend the 53# and 35# (one each) That's about $150. You can find routines on line that will kick your ass. Heck, you might even be able to use your concrete buckets for some of the work outs. You can also look for used, which brings me to...
Craigslist/Facebook Marketplace: This is the place to look for power(squat) racks, benches, bars, etc. (and kettlebells) for cheap. Look around, and you should be able to get a power rack, bench, 7' bar and ~300-400# of weights for about $500. Don't pay more than $0.50/lb for plates. I've built garage/basement gyms (twice) for about $500 (power rack, bench, barbell, weights), then added what I wanted. All you really need is the rack, a barbell and plates - now you can squat, deadlift, power cleans, overhead presses, pull ups (on the rack). For chest just do pushups until you get a bench (you can also do them in the rack laying on the floor.
I know money is tight for you, but these are suggestions for the future. Good luck!