Account limits apply only for fiat deposits. 
The 1M sats max looks like an artificial restriction on LNURL only, we can bump it if needed. 
Our API allows a max of 1M USD into a fiat balance. 
Receiving into BTC balance should be unlimited (of course LN invoices are unsuitable for large amounts). 

lnbc1000001pn8lnxypp58la07a5h0vuu2ayq87fvwjd7jq8q6rd92sladm7njyaytd5ka2ssdpqf3shyem9ypfhgunfddjjq6twwehkjcm9cqzzsxqrrs0sp5529mgxhxkqyqe9ckts7mhv6junww5wau9mhdcn6xk0e7dtuqnces9qyyssqpmek6rdvfkvhxd7xgkzwpjnr4g02dtg0zqkwgykpfse5kfllytczlcjqr2ej23yw57n6e9nyc2fj5rn63crx5vtz8aw7mskycy25rvgpzkkhr3