What's the best financial institution to get a loan based on pledged stock assets?

Here's my situation. I've got about $900K in a non-IRA (Schwab) in an Irrevocable Trust (I'm the sole Beneficiary & Trustee if that matters - the Trust itself is complex, but pretty much allows me to do what I want with it). I want to get a line-of-credit loan of perhaps $150K, that I plan on paying off from an inherited Roth distribution (where I have about $700K) whenever I feel like it's time to ring the register on some position there. Even though I would love to ring the register on some of those positions that are now (or soon will be) long-term unrealized gains, because I want to keep my ACA MAGI income at 150% of poverty to get a heavily subsidized Silver-94% plan, I can't extract the gains (indeed, some of these gains are 6X, so most of the proceeds would be gains), and so they are basically frozen until I get on Medicare (i.e., the combination of the lowered subsidies from an increase in income past 150% would be equivalent to a 25% implicit tax rate). (I could retain the income in the Trust, but that would be at a 23.8% haircut - 20% long-term cap-gains + 3.8% ACA tax - oh, the irony, LOL) If it matters, this $150K is to be used to pay for construction of a house (for my personal residence use) on a property that the Trust owns.

I could just simply extract the cash in a regular margin from Schwab, but the interest rate is ridiculous (like 11%). I think the margin is at IBKR is around 5.25%, but I wonder if I can have a Trust account there, as well as them having not-so-good service - although since I wouldn't be doing much, I guess it wouldn't be a big thing. Any transfer would be to my Trust non-IRA (actually checking account associated with the Trust non-IRA) at Schwab, which is the account that I would be using to spend the money.

I was talking to a friend of mine that has some assets at USB, and he got something like 6% on a loan (although this wasn't a Trust account) - and so I was thinking that some big bank might be in a better situation to give me a better loan. I would tend to think that since this would be a loan with the Trust as the borrower, my own financial situation is irrelevant (for the record, my credit score is A+, but of course, my official income is very low, LOL).